QC 


\F006169 


KuppFER's  VESICLE 


AND  ITS 


RELATION  TO  GASTRULATION  AND 
CONCRESCENCE, 


FRANCIS  BERTODY  SUMNER. 


[Reprinted  from  Memoirs  New  York  Academy  of  Sciences,  Volume  II,  Part  II,  J900.1 


Submitted    in   partial   fulfillment  of  the   requirements   for 

the    Degree    of  Doctor  of   Philosophy  in    the    Faculty   of 

Pure  Science,  Columbia  University 


EXCHANGE 


NEW  YORK   ACADEMY   OF   SCIENCES. 
MEMOIRS,  VOLUME  II,  PART  II,  1900. 


ARTICLE  III. 


VESICLE 


AND    ITS 


RELATION  TO  GASTRTJLATION  AND 
CONCRESCENCE. 


FRANCIS   BERTODY   SUMNER. 


TEXT   FIGURES   1-34. 


NEW   YORK : 
PUBLISHED  BY  THE  ACADEMY. 


Submitted    in  partial  fulfillment  of  the   requirements   for 

the   Degree    of  Doctor  of  Philosophy  in    the   Faculty  of 

Pure  Science,  Columbia  University 


JLOGY 

LIBRARY 

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PRESS  OF 

THE  NEW  ERA  PRINTING  COMPANY 
LANCASTER,  PA. 


!-»»• 


[New  York  Academy  of  Sciences.     Memoirs,  Vol.  II,  Part  II,  pp   47  to  83,  October  15,  1900.] 


FRANCIS   BERTODY  SUMNER 

BORN  AUGUST    i,    1874. 

MINNEAPOLIS  ACADEMY,    1887-1890. 
UNIVERSITY  OF  MINNESOTA,  B.  S.,  1894. 

Scholar  in  Animal  Biology,    1893-1894. 
State  Natural  History  Survey,  1892-1893. 
University  Fellow,    1894. 

COLUMBIA  UNIVERSITY,  1895—1901. 

University  Scholar,   1897-1898. 

John   D.   Jones  Scholar,   1898. 

Senff  Zoological  Expedition  to  Egypt,    1899. 

University  Fellow,    1899,   (resigned.) 

University  Table  at  Naples  Zoological  Station,    t&$ 

Tutor  in  Natural  History  in  the   College   of  the   City   of  New 
York,   1899. 

Member  of  New  York  Academy  of  Sciences. 


X.  NOTE  ON  METHODS ...TTTTTTTrrrrr^TTTTTTTTTT         T5~ 

XI.  SUPPLEMENT 79 

BIBLIOGRAPHY.  . .  80 


299288 


BIOLOGY 
LIBRARY 

G 


[New  York  Academy  of  Sciences.     Memoirs,  Vol.  II,  Part  II,  pp   47  to  83,  October  15,  1900.] 


KUPFFER'S  VESICLE  AND   ITS  RELATION  TO  GASTRULATION  AND 

CONCRESCENCE. 

FRANCIS  BERTODY  SUMNER. 

(Read  February  12,  1900.) 

[Text  figures  1-34  ] 

CONTENTS. 

PAGE 
INTRODUCTION 

I.  THE  TELEOST  GASTKULA 48 

Gotte's  view 

A  new  factor 50 

II.  KUPFFER'S  VESICLE  52 

The  prevailing  view 52 

Relation  of  Kupffer's  vesicle  to  the  "  Prostomal  thickening" 53 

Kowalewski's  account  of  Kupffer's  vesicle 53 

Conclusive  evidence  of  the  preceding  view 54 

Previous  observations  of  a  similar  nature 55 

Condition  in  Amia 57 

III.  RELATION  OF  PROSTOMA  TO  GERM  LAYERS 59 

Prostomal  thickening  and  gut-hypoblast    59 

The  relation  of  the  gut  epithelium  to  the  notochord 60 

Historical 61 

IV.  SIGNIFICANCE  OF  PROSTOMAL  INVAGINATION 62 

V.  CONCRESCENCE  AND  CONFLUENCE 68 

Problem  stated 68 

Experiments  of  Morgan  and  Kopsch '. 70 

Conclusions 72 

VI.  FURTHER  MORPHOLOGICAL  CONSIDERATIONS 73 

VII.  YOLK  VESICLES 74 

VIII.  THE  FUNCTION  OF  KUPFFER'S  VESICLE 76 

IX.  RECAPITULATION 77 

X.  NOTE  ON  METHODS 78 

XI.  SUPPLEMENT 79 

BIBLIOGRAPHY....  80 


299288 


48  MEMOIRS  OF  THE  NEW  YORK  ACADEMY  OF  SCIENCES 

INTRODUCTION. 

This  paper  is  the  outcome  of  observations  carried  on  during  the  past  few  years 
in  the  Zoological  Laboratory  of  Columbia  University,  in  the  Marine  Biological  Lab- 
oratory at  Wood's  Holl,  in  the  John  D.  Jones  Laboratory  at  Cold  Spring  Har- 
bor,1 in  the  Stazione  Zoologica  at  Naples,  and  finally  in  the  Department  of  Natural 
History  in  the  College  of  the  City  of  New  York.  I  owe  much  to  the  help  of  those 
in  charge  of  each  of  the  laboratories  named,  being  especially  grateful  to  Profes- 
sor BASHFORD  DEAN  for  his  constant  interest  in  my  work,  his  ever-ready  assistance, 
and  his  many  valuable  suggestions.  I  also  take  pleasure  in  acknowledging  the  gen- 
erous aid  given  me  by  Professor  ULRIC  DAHLGREN,  of  Princeton  University,  to 
whom  I  owe  my  success  in  obtaining  the  eggs  of  Noturus ;  and  in  expressing  my  ap- 
preciation of  the  help  and  advice  given  me  by  Doctor  PAUL  MAYER  at  Naples,  as 
well  as  of  the  valuable  material  procured  through  the  efforts  of  Doctor  Lo  BIANCO. 
The  eggs  of  Salvelinus  I  owe  to  the  kindness  of  Mr.  CHARLES  WALTERS,  of  the  New 
York  State  Fish  Hatchery  at  Cold  Spring  Harbor,  and  to  the  courtesy  of  the  U.  S. 
Fish  Commission. 


I.     THE  TELEOST   GASTRULA. 

Gotte's  View. — The  account  of  gastrula  formation  in  the  teleost  advanced  by 
GOTTE  ('73 — his  main  idea  had  been  briefly  presented  four  years  before)  has  been 
accepted  by  the  majority  of  investigators  in  this  field.  Although  it  is  now  a  com- 
monplace to  embryologists,  I  shall  introduce  this  discussion  by  a  brief  statement  of 
GOTTE'S  view,  since  it  is  my  object  to  prove  that  this  view  must  be  amended  in  one 
very  important  particular. 

FIGURE  1. 


Figures  1  to  4  (A  and  B)  illustrate  the  orthodox  account  of  gastrula  formation. 
They  show  the  teleost  blastoderm,  in  surface  view  and  in  section,  at  four  different 

.  '  As  John  D.  Jones  Scholar  of  Columbia  University. 


SUMNER:    KUPFFER'S  VESICLE 


49 


stages  of  development.  Figure  1  represents  the  early  segmented  germ-disc.  In  the 
stage  shown  in  figure  2  the  blastoderm  has  increased  in  area  but  diminished  in 
thickness,  and  a  thin  superficial  layer  of  cells  ("  Deckschicht,"  GOTTE)  has  become 
differentiated.  In  the  stage  shown  in  figure  3  an  important  change  has  taken  place 
in  the  relative  thickness  of  the  parts.  The  central  region  has  become  thinner,  both 
relatively  and  absolutely,  while  the  marginal  region  is  now  thicker.  The  natural 

FIGURE  2. 


inference  is  that  a  part  of  the  central  cells  have  migrated  peripherad,  and  this  is  the 
inference  drawn  by  GOTTE.  This  thickened  marginal  region  is  called  by  GOTTE 
"Randwulst"  (von  Baer).  It  is  seen  in  the  figure  that  the  superficial  layer 
("  Deckschicht ")  extends  a  trifle  beyond  the  cells  of  the  marginal  wall  and  that 
its  border  rests  directly  on  the  yolk,  leaving  a  small  space,  triangular  in  section, 
around  the  margin.  Finally  in  figure  4,  gastrulation  is  shown  in  progress.  From 
the  marginal  wall  a  projecting  ledge  of  cells  is  growing  inward  over  the  yolk.  This 
process  begins  on  one  side  of  the  blastoderm  (the  future  posterior  end  of  the  embryo) 


FlOUEE  3. 


but  soon  extends  to  the  whole  circumference,  although  remaining  most  conspicuous 
on  the  embryonic  side.  Figure  4,  A,  represents  a  blastoderm  of  this  stage  as  seen 
in  surface  view.  The  invaginate  layer  ("  Secundiire  Keimschicht,"  GOTTE)  is  seen  to 
take  the  form  of  a  diaphragm  with  an  excentric  and  not  quite  circular  aperture.  The 
"  Deckschicht,"  as  before,  ends  freely  on  the  yolk.  Figure  4,  B,  is  a  section  cut  in 
the  plane  of  the  dotted  line  in  A. 


50 


MEMOIRS  OF   THE   NEW   YORK    ACADEMY   OF  SCIENCES 


As  to  the  mechanics  of  the  process,  GOTTE  maintained  that  the  same  peripherad 
movement  of  the  cells  which  produced  the  "  Randwulst "  produced  an  involution  of 
the  margin  to  form  the  "  Secundiire  Keimschicht,"  and  led  to  the  growth  of  the  lat- 
ter centrad. 

Although  other  writers  have  held,  and  probably  with  truth,  that  at  least  in 
some  cases,  the  secondary  layer  is  formed  wholly  or  in  part  by  ddamination  from  the 
germ-wall,  nearly  all  ernbryologists  are  agreed  that  the  end  result  is  as  shown  in 
figure  4.  A  circular  sheet  of  cells,  inflected  at  its  margin,  and  covered  by  a  pave- 
ment layer  which  does  not  share  in  this  inflection — such  is  their  teleost  gastrula. 
According  to  this  view  the  germ-ring  or  inflected  layer  represents  the  entire  hypo- 
blast  and  mesoblast  of  the  embryo. 

A  New  Factor. — One  object  of  the  present  paper  is  to  show  that  the  above 
conception  of  gastrulation  in  the  teleost,  although  in  large  degree  true,  fails  to 

FIGURE  4. 


recognize  a  highly  important  factor.     The  fish  gastrula  presents  a  far  more  complex 
structure  than  the  scheme  of  Gotte  contemplated. 

More  than  a  year  ago,  in  a  paper  before  the  American  Morphological  Society 
(December  28,  1898)  the  writer  described  for  the  cat-fish  blastoderm  a  pronounced 
thickening  of  the  pavement  layer  ("  Deckschicht ")  on  the  embryonic  (posterior) 
margin  of  the  blastoderm.  Although  stating  that  this  structure  was  of  constant 
occurrence,  I  was  at  that  time  unable  to  offer  an  opinion  as  to  its  significance.  I 
have  later  devoted  a  great  deal  of  attention  to  this  question  and  have  discovered 
this  same  problematic  cell-mass  in  a  considerable  number  of  fishes  belonging  to 
widely  different  families.  In  all  these  cases,  the  origin  and  fate  of  this  cell-mass 
appears  to  be  the  same.  It  is  perhaps  most  readily  observed  in  the  trout ;  but 
although  this  fish  has  long  been  a  classical  object  for  embryological  study,  the 
appearances  which  I  am  about  to  describe  have  been  noticed  by  only  one  previous 
writer  (Berent,  '96). 1 

1  BERKNT'S  observations  were  quite  incomplete  and  his  interpretations  entirely  incorrect.  Even  GREGORY  ('99) 
the  latest  of  those  who  have  discussed  the  early  development^  of  the  trout,  has  missed  the  point  as  completely  as  any  of 
his  predecessors. 


SUMNER  :    KUPFFER'S  VESICLE 


51 


Figure  5  represents  a  sagittal  section  through  an  early  blastoderm  of  the  brook 
trout  (Salvelinus  fontinalis),1  absolute  age  unknown.  One  of  the  most  obvious  and 
striking  facts  is  the  condition  of  the  pavement  layer  at  the  posterior  (embryonic) 
margin.  Its  cells,  instead  of  being  thin  and  flattened  as  elsewhere,  are  here  elon- 
gated in  a  vertical  direction.  The  surface  of  the  blastoderm  at  this  point  is  notice- 


FlOURE  5. 


Pr, 


^M^^v^l^/^^ 


•?:>:  i&Jsffi£*'s'$<  &  *' -:J>^">i '^'M'^W 
'.'•ri^y*'. ^.y.'a-if^-^-'w-.r  •>;  '•/J>^:-;.  -•  .< /"..-:^s^.i{, 

W^®iiKfe;:  ^" 


After  camera  lucida  drawing.     Pr,  thickening  of  pavement  layer  at  posterior  border. 

ably  indented,  and  the  arrangement  of  the  cells  with  reference  to  the  indentation  is 
such  as  to  strongly  suggest  an  invagination  occurring  here.  The  line  separating  the 
"  Prostomal  Thickening,"  as  I  shall  henceforth  call  this  proliferation  of  the  super- 
ficial layer,  and  the  underlying  cells  of  the  blastoderm  is  not  at  all  clear  in  this 


FlGtTEE    6. 


Pr 


Sagittal  section  (after  camera  Incida  drawing) — showing  condition  in  Snleelinus  blastoderm  considerably 

more  advanced  than  that  shown  in  Figure  5. 

section.    The  deeper  stain  of  the  superficial  cells  nearly  disappears  as  we  pass  inward 
from  the  surface. 

At  a  somewhat  later  period  (a  day  or  less  older)  the  germ-ring  is  well  established. 
It  will  now  be  seen  (figure  6)  that  the  "  prostomal"  mass  of  cells  is  continued  for- 
ward into  a  thin  layer  underlying  the  cells  of  the  germ-ring  proper. 

1  It  cannot  be  objected  that  the  difference  may  be  due  to  my  having  studied  a  different  species  of  trout,  since,  as  we 
shall  see,  the  condition  described  seems  to  be  a  universal  one  among  the  Tdeontei. 


52 


MEMOIRS  OF  THE  NEW   YORK   ACADEMY   OF  SCIENCES 


II.     KUPFFER'S    VESICLE. 

The  Prevailing  View. — In  the  present  paper  I  cannot  enter  into  a  complete 
historical  review  of  this  subject.  KUPFFER'S  own  conception  of  this  structure  we 
shall  consider  later.  In  the  meantime,  I  shall  state  briefly  the  accounts  given  by 
AGASSIZ  and  WHITMAN  ('84)  who  first  satisfactorily  described  the  condition  in  the 
pelagic  type  of  egg  and  by  HENNEGUY  ('88)  who  was  a  pioneer  worker  in  this  line 
upon  the  trout.  AGASSIZ  and  WHITMAN  observed  in  the  pelagic  egg  of  Ctenolabrus, 
a  number  of  small  vacuoles,  appearing  in  the  periblast  beneath  this  region  of  the 
embryo.  These  vacuoles  soon  united  into  one  (so  much  had  already  been  observed 
by  KINGSLEY  and  CONN,  '83)  and  above  it  the  cells  of  the  embryo  began  to  arrange 
themselves  as  a  columnar  epithelium  which  arched  over  this  cavity.  In  the  case  of 
the  trout  embryo,  HENNEGUY  states  that  the  formation  of  the  vesicle  is  preceded  by 


FIGURE  7. 


FIOUKE  8. 


Section  showing  fully  formed  Kupffer's 
Vesicle  in  the  trout  (after  Henneguy). 


KV. 


Embryo  of  Clenolabrus,  showing  fully  formed  Kupf- 
fer's Vesicle.  Kv,  |Kup£fer's  Vesicle,  GHy,  gut-hypo- 
blast. 


a  radial  arrangement  of  certain  cells  in  the  posterior  undifferentiated  region  of  the 
embryo.  A  cavity  then  forms  in  the  midst  of  these  cells,  thus  giving  rise  to  the 
vesicle. 

Figure  8  is  drawn  from  one  of  my  own  preparations  of  Cienolahrws.  AGASSIZ 
and  WHITMAN  give  no  satisfactory  figures,  although  their  description  is  clear. 
Figure  7  is  taken  from  HENNEGUY'S  paper  on  the  trout.  Both  of  these  figures 
represent  the  vesicle  in  its  fully  developed  condition.  They  differ  in  that  the  vesicle 
of  the  trout  is  from  the  first  completely  bounded  by  cells,  while  in  the  pelagic  egg 
the  cellular  wall  is  not  complete.  But  the  accounts  agree  in  representing  the  waP 
of  the  vesicle  as  differentiating  in  situ  from  a  homogeneous  mass  of  cells  without 
reference  to  any  preexisting  (cellular)  structure. 

It  is  now  well  established  that  both  types  of  Kupffer's  Vesicle  as  above  figured 
actually  occur  :  the  question  as  to  which  type  is  more  primitive  will  be  considered 
later.  Both  of  the  above  accounts,  although  true  as  far  as  they  go,  are  incomplete 


SUMNER:   KUPFFER'S  VESICLE  53 

in  so  far  as  they  neglect  the  first  steps  in  the  formation  of  this  interesting  structure 
and  leave  out  of  consideration  certain  phenomena  of  high  theoretical  importance. 

Relation  of  Kupffer's  Vesicle  to  the  "Prostomal  Thickening." — To  return 
to  Salvelimis—at  a  stage  considerably  later  than  that  shown  in  figure  6,  we  have  the 
condition  represented  in  figure  9,  which,  like  the  preceding  figures,  is  drawn  from  a 
median  longitudinal  section  of  the  embryo.  In  the  anterior  portion  of  the  section 
there  are  three  layers,  not  counting  the  overlying  pavement  layer,  viz.  : — dorsally, 
the  neural  axis,  ventrally  the  single  layer  of  gut-hypoblast,  and  between  the  two, 
the  disc-shaped  cells  on  the  notochord.  The  neural  and  chordal  portions  lose  their 
identity  caudad  in  a  homogeneous  cell-mass.  The  ventral  layer  is  continued  back- 
ward into  one  or  both  walls  of  Kupffer's  Vesicle.  The  condition  caudad  to  the 
vesicle  is  less  clear.  It  seems  certain,  however,  that  at  this  stage  there  is  no  distinct 
ventral  layer  extending  to  the  posterior  margin. 

The  position  of  this  vescicle  strongly  suggests  that  it  bears  some  relation  to  the 
mass  of  cells  which  we  have  discussed  under 
the  designation  of  "  prostomal  thickening." 
Its  walls  are  one  or  both  continued  cephalad 
into  the  thin  layer  of  gut  hypoblast  under- 
lying the  chorda.  Moreover,  this  prostomal 
cell-mass,  unless  it  be  represented  by  the 
walls  of  the  vesicle,  has  quite  lost  its  iden- 

.  Posterior  end  of  sagittal  section  of  brook  trout 

tlty.        Lhe    most    Conclusive   evidence    I    shall       embryo  (camera  lucida  drawing).     Kv,  Knpffer's 

defer,  however,  until  I  have  entered  into  a      Veaicle:  ^,  neural  axis;  Ch,  notochord;  any, 

gut-hypoblast. 

brief  historical  discussion.      Let  us  consider 

whether  the  structure  herein  termed  "  prostomal  thickening  "  has  been  previously 

observed. 

Kowalewski's  Account  of  Kupffer's  Vesicle. — M.  VON  KOWALEWSKI  described 
in  Carassius  a  mass  of  cells,  triangular  in  section,  lying  at  the  posterior  margin  of 
the  embryo  and  bounded  by  the  pavement  layer,  the  marginal  wall  and  the  periblast. 
Except  at  this  point,  the  pavement  layer  spanned  a  narrow  space  and  ended  freely  on 
the  yolk  as  above  represented.  In  his  first  paper  (KOWALEWSKI  '85)  he  considered 
this  cell-mass  to  be  the  rudiment  of  the  whole  entoderm,  considering  the  cells  of  the 
germ-ring  to  be  purely  mesodermal  in  their  fate  (he  asserted  this  same  view  in  his 
next  paper,  '86,  a).  Later  ('86,  b)  he  modified  his  view  to  the  effect  that  it  repre- 
sented only  that  part  of  the  entoderm  forming  the  walls  of  Kupffer's  Vesicle.  The 
latter,  according  to  KOWALEWSKI,  was  a  part  of  the  archenteron,  and  the  cord  of 
cells  which  he  figures  (figure  10,  B)  as  extending  backward  from  below  the  vesicle 


54 


MEMOIRS  OF   THE   NEW  YORK   ACADEMY  OF  SCIENCES 


was  the  solid  rudiment  of  the  neurenteric  canal.  The  radial  arrangement  in  this 
problematic  cell-mass  at  an  earlier  stage  (figure  10,  A)  suggested  to  him  an  in  vagi- 
nation,  and  he  considers  this  to  be  the  equivalent  of  the  "  prostoma  "  of  KUPFFER, 
differing  from  it  only  in  that  the  latter  opened  directly  to  the  surface  instead  of 
being  covered  by  the  superficial  layer.  Kupffer's  Vesicle  represents,  according  to 

FIGURE  10. 


A.  Sagittal  section  through  posterior  border  of 
blastoderm  of  Carassius  (after  Kowalewski)  show- 
ing supposed  invagination  occurring  at  this  point. 


B.   Section  showing  Kupffer's  Vesicle  in  Caras- 
sius (after  Kowalewski). 


FIGURE  11. 


KOWALEWSKI,  a  small  but  important  part  of  the  "  Gastruladarm,"  the  rest  of  which 
is  represented  by  the  uncovered  part  of  the  yolk. 

It  is  surprising,  in  view  of  this  brief  and  accurate  description  presented  as  long 
ago  as  1886,  that  the  prostomal  thickening  has  been  all  but  ignored  by  subsequent 
investigators.  Both  HENNEGUY  ('88)  and  VIRCHOW  ('95)  have  seen  cells  in  this  po- 
sition, but  do  not  regard  them  as  being  of  constant  occurrence  nor  of  any  theoret- 
ical importance.  (Concerning  BERENT,  see  below.) 

Conclusive  Evidence  of  the  Preceding  View.— The 
present  writer  first  noticed  the  prostomal  mass  of  cells  in 
the  blastoderm  of  Amiurus  (figure  11),  regarding  it  at  the 
time  as  a  mere  thickening  of  the  superficial  layer.  Upon 
following  out  the  subsequent  course  of  development  and 
comparing  with  the  condition  in  other  forms,  I  was  led  to 
a  view  of  its  significance  quite  similar  to  that  expressed  in 
KOWALEWSKI'S  later  paper,  even  before  I  had  seen  the  lat- 
ter. The  presence  of  the  nick  or  indentation  often  found 
in  this  cell-mass,  and  the  grouping  of  its  cells  (figures  5  and  10,  A)  have  been  noted 
by  KOWALEWSKI  and  offered  by  him  as  an  evidence  of  invagination.  Another  ap- 
pearance, which  I  noticed  in  an  embryo  of  Amiurus  at  the  time  of  the  formation  of 
Kupffer's  Vesicle  (figure  12)  pointed  to  an  obvious  relation  between  this  vesicle  and 
the  supposed  invagination.  In  a  paper  before  the  New  York  Academy  of  Sciences 
('99,  b)  I  advocated  a  view  similar  to  that  of  KOWALEWSKI.  As  then  stated,  my 
opinion  was  somewhat  different  from  that  presented  in  the  present  paper. 

The  chain  of  evidence  was  not  complete,  however,  until  a  form  had  been  found 


Pr 


Section  showing  thickening  of 
superficial  layer  (Pr)  on  pos- 
terior margin  of  early  Amiurus 
blastoderm. 


SUMNER:    KUPFFER'S  VESICLE 


55 


FIGURE  12. 


which  showed  an  open  invagination  in  place  of  the  solid  ingrowth.  The  hypo- 
thetical primitive  condition  was  shown,  with  diagrammatic  distinctness,  in  the  egg 
of  an  unknown  eel  (Mttraenaf),  which  it  was  my  good  fortune  to  secure,  while  at 
Naples,  during  the  summer  of  1899.1 

Here,  as  in  the  preceding  forms,  the  process  is 
initiated  by  a  thickening  and  indentation  of  the 
superficial  layer  on  the  embryonic  side  of  the  blast- 
oderm margin  (figure  13).     The  next  ensuing  stage 
is  represented  in  figure  14,  which  demands  little  ex- 
planation.     Figure    13   represents   the   condition 
when  the  blastopore  is  still  large,  while  in  the  next 
stage  only  a  slender  yolk-plug  remains.    The  Vesicle 
of  Kupffer  has  meanwhile  attained  a  considerable 
size,  so  that  it  is  readily  visible  in  the  living  egg. 
In  the  latter  there  is  also  to  be  seen  a  fine  canal  con- 
necting the  vesicle  with  the  exterior,  through  the  blastopore,  and  passing  just  in  front 
of  the  yolk-plug.     This  condition  is  quite  enduring,  lasting  for  perhaps  an  hour  after 
the  appearance  of  the  vesicle  to  view  in  the  living  eggi     Sagittal  sections  removed 
any  possible  doubt  as  to  the  meaning  of  -this  appearance.     Here,  as  in  the  forms 

FIGURE  13. 


Posterior  eiid  of  very  early  Amiurus  em- 
bryo (cam.  lac.)  showing  interesting  rela- 
tion between  superficial  layer  of  the  epiblast 
aud  the  vesicle. 


Sagittal  section  through  blastopore  region  of  early  Murxnaf  embryo  (cam.  Inc.). 

previously  discussed,  there  is  a  direct  continuity  between  the  invaginated  cell-layer 
and  the  lowermost  layer  of  the  embryo. 

Previous  Observations  of  a  Similar  Nature. — It  is  interesting  to  note  that 
this  manner  of  formation  of  Kupffer's  Vesicle  through  an  invagination  from  above 
is  identical  with  that  described  by  KUPFFER  himself  in  1879.  The  latter  author 
came  to  this  conclusion  from  the  study  of  the  living  eggs  of  Osmems  (see  figure  15) 

1  In  a  paper  read  before  the  last  session  of  the  American  Morphological  Society  ( New  Haven,  December  27, 
1899),  I  described  this  case,  and  referred  to  the  egg  as  being  that  of  Murasna.  I  have  later  learned  from  Dr.  LoBianco 
that  he  is  uncertain  of  the  genus. 


56 


MEMOIRS  OF  THE  NEW  YORK   ACADEMY  OF  SCIENCES 


and  the  pike  (later  also  of  the  trout).1  KUPFFER  says  that  he  confirmed  these  obser 
vations  by  sections,  though  none  are  figured.  Curiously  enough  KUPFFER'S  state- 
ments on  this  subject  have  been  discredited  by  the  majority  of  later  investigators, 
though  they  have  been  confirmed  by  a  few.  Professor  DOHRN  informs  me  that  he 
years  ago  noted  the  open  connection  in  the  case  of  the  perch  but  had  never  pub- 


FlQUEE   14. 


FIGURE  15. 


EC 

Contiguous  sections  of  Murxna  t  embryo  cut  as  above— somewhat  later  than  preceding  (camera  lucida  drawings). 
Pr,  "  prostoma  "  ;  Yp,  yolk-plug  ;  Kv,  Kupffer's  Vesicle  ;  GBy,  gut-hypoblast ;  NeHy,  "  non-embryonic  "  hypoblast ; 
EC,  cells  embedded  in  periblast. 

lished  this  observation.  HENNEGUY  ('88)  noticed  this  condition  in  the  case  of  the 
same  fish  but  later  concluded  that  he  had  been  in  error.  He  did  not  deny,  how- 
ever, the  possible  accuracy  of  Kupffer's  observation.  RAFFAELLE  ('88)  observed  in 
the  living  egg  of  Uranoscopus  and  in  an  unknown  pelagic  egg  that  KupfFer's  Vesicle 
was  for  a  brief  period  connected  with  the  exterior  through  the  blastopore.  This 
connecting  passage  he  regarded  as  equivalent  to  the  neuren- 
teric  canal.  MC!NTOSH  and  PRINCE  ('90)  also  speak  of  "what 
seems  to  be  a  tubular  connection  of  the  external  blastopore  and 
I  pr  the  ventral  surface  of  the  embryo"  but  cannot  be  sure  of  an 
open  passage  into  Kupffer's  Vesicle.  As  none  of  these  authors 
sectioned  the  eggs,  we  do  not  know  whether  the  canals  described 
had  cellular  walls  or  merely  lay  in  the  periblast.  The  "linear 
Optical  section  of  egg  of  canal"  mentioned  by  AGASSIZ  and  WHITMAN  ('84)  was  evi- 
dently  meYely  the  disaPPearing  blastopore. 

There  is  then  every  reason  to  believe  that  the  open  invagina- 
tion  occurring  in  Murse.no,  f  and  probably  certain  other  fishes  is  represented  by  the 
ingrowing  cell-mass  found  by  Kowalewski  in  Carassius  and  Gobius  and  by  myself  in 
Amiurus,  Noturus,  Salvelinus,  Fundulus  and  Ctenolabrus.  The  presumption  is  that  the 
solid  condition  is  the  more  frequent  among  the  teleosts.  This  masked  form  of  invagina- 

'The  vesicle  was  first  described  by  KUPFFER  in  1866  in  the  embryos  of  Gasterosteus  and  Goliius.  Its  origin  by  in- 
vagination  was  not  at  that  time  maintained.  SOBOTTA  ('98)  states  that  COSTE  had  figured  the  vesicle  in  1847.  LERE- 
BOULLET  also  ('63,  figure  22)  represents  what  appears  to  be  Knpffer's  Vesicle. 


(v-  • 
Of  THE 
UNIVERSITY 


SUMNER:    KUPFFER'S  VESICLE 


57 


FIOUKE  16. 


SI 


tion  is  quite  characteristic  of  the  bony  fishes,  as  witness  the  neural  axis  and  auditory 
and  optic  vesicles.  The  later  appearance  of  the  cavity  of  Kupffer's  Vesicle  is 
strictly  comparable  with  the  delayed  formation  of  the  neural  canal  or  the  cavities  of 
the  sensory  vesicles. 

It  may  be  objected  that  the  sort  of  Kupffer's  Vesicle,  described  for  Ctenolabrus 
and  other  pelagic  eggs,  in  which  a  cellular  floor  is  wanting,  is  not  reducible  to  the 
above  type.  But  as  already  stated,  I  find  in  Cteno- 
labrus a  typical  prostomal  thickening,  and  I  cannot 
regard  the  fact  that  these  cells  do  not  completely 
surround  the  cavity  as  of  any  importance  to  the 
theory.  I  shall  later  give  reasons  for  believing 
that  this  condition  is  a  retrograde  one. 

Condition  in  Amia. — Now  is  this  condition  in 
the  teleosts  a  unique  one  or  do  we  find  a  counter- 
part in  any  other  group  ?  Dean  has  strongly  main- 
tained that  the  key  to  teleost  development  is  to  be 
found  among  the  ganoids,  and  from  the  generally 
accepted  phylogenetic  relation  of  the  two  groups, 
this  proposition  seems  self-evident. 

It  was  DEAN'S  endeavor  (DEAN,  '95,  '96)  to  show 
that  the  ganoids,  in  their  mode  of  development  held 
a  middle  position  between  the  elasmobranchs,  on  the 
one  hand,  and  the  teleosts  on  the  other.  My  own 
observations  as  far  as  they  go,  sustain  this  view.  As 
regards  the  special  subject  of  the  present  paper, 
DEAN  described  in  the  eggs  of  Acipenser,  Lepidosteus 
and  Amia,  what  he  considered  to  be  the  homologue 
of  Kupffer's  Vesicle  in  the  teleosts.  This  was  a 
cavity  beneath  and  slightly  anterior  to  the  dorsal 
lip  of  the  blastopore,  bounded  above  and  behind  by 
the  cells  of  the  latter,  below  by  the  yolk.  DEAN 
maintained  that  this  cavity  simply  represented  the 
angle  formed  by  the  blastoderm  margin  as  it  was 
mechanically  turned  in  upon  itself  during  its  circumcrescence  of  the  yolk.  This 
simple  mechanical  explanation  I  cannot  accept  for  the  teleosts  because  (among  other 
reasons)  the  vesicle  in  some  fishes  is  not  formed  until  the  blastoderm  has  nearly  or 
quite  finished  its  journey  over  the  yolk  (Muravna  ?  Perca)  and  thus  the  supposed 


Blastopore  region  of  Amia  cut  in  sagittal 
plane  (slightly  schematized  from  camera 
lucida  drawing).  Yc,  yolk  cells;  Sy,  yolk 
syncytium;  TV,  "  prostoraa  " ;  81,  superfi- 
cial layer  of  epiblast. 


58 


MEMOIRS  OF  THE  NEW  YORK  ACADEMY  OF  SCIENCES 


mechanical  cause  no  longer  exists.  But  I  believe  that  the  homology  proposed  by 
DEAN  is  well  founded.  Through  Professor  DEAN'S  kindness,  I  have  had  the  privilege 
of  studying  some  fine  Amia  material,  and  have  found  therein  the  counterpart  of  the 
phenomena  just  described  for  the  teleosts. 

Figure  16  shows  a  longitudinal  (nearly  or  quite  sagittal)  section  through  the 
egg  of  Amia  at  a  time  when  the  yolk-cells  are  perhaps  three-quarters  covered.  The 
superficial  layer  of  the  epiblast  is  seen  to  be  much  thicker  at  the  blastopore  margin 
than  elsewhere  and  to  be  directly  continuous,  around  the  margin,  with  the  inner- 
most germ-layer.  This  condition  occurs  upon  the  entire  periphery,  but  on  the  dor- 
sal (embryonic)  side  of  the  blastopore  the  case  is  somewhat  more  complicated. 
Here  we  find  an  arrangement  strictly  comparable  to  that  found  in  figure  13.  In 
both  there  is  an  enormous  development  of  the  pavement  layer  at  the  caudal  end  of 

the  embryo  and  an  indentation  of  its 

FIGURE  17. 

p  Q 


N  6  H  V 

1      *».— 


Sy     GHy'"  *^ 

Blastopore  region  of  Amia  after  closure  (drawn  as  preceding). 
Up,  blastopore;  Ne  Hy,  "non-embryonic"  hypoblast;  GHy, 
gut-liypoblast ;  Kv,  probable  homologue  of  Kupffer's  Vesicle  ; 
Sy,  rudimentary  syncytium. 


surface  around  which  the  cells  are 
arranged  in  radial  manner.  In  one 

O 

respect,  hoAvever,  this  Amia  embryo 
exhibits  a  more  advanced  condition 
than  that  of  the  Murasnaf  embryo 
shown  in  figure  13.  The  notch  in 
the  pavement  layer  is  seen  to  be  con- 
tinued cephalad  into  a  very  notice- 
able cleft,  extending  forward  for  some 
distance  into  the  hypoblast  and  sep- 
arating it  into  two  layers. 


"Again  the  similarity  between  figures  17  and  14  is  evident.  The  chief  difference 
between  the  two  seems  to  be  that  in  the  former  there  is  wanting  the  open  canal,  con- 
necting the  cavity  of  the  vesicle  with  the  exterior  which  occurs  in  the  latter.  This 
open  canal  is  wanting  even  in  embryos  slightly  younger  than  that  shown  in  figure 
17,  but  the  obliteration  of  its  lumen  is  surely  a  matter  of  secondary  importance. 
The  ganoidean  homologue  of  Kupffer's  Vesicle,  like  that  of  many  teleosts,  has 
a  ventral  wall.  This  is  well  developed,  though  not  quite  complete,  consisting  of  a 
layer  of  pavement-like  cells,  lying  directly  upon  the  large  yolk  cells.  This  condi- 
tion has  not  been  mentioned  by  either  DEAN  ('96)  or  SOBOTTA  ('96). 


SUMNER:   KTJPFFER'S  VESICLE  59 


III.  RELATION  OF  PROSTOMA  TO  GERM  LAYERS. 

Prostomal  Thickening  and  Gut-Hypoblast. — The  exact  part  played  by  the 
prostomal  cells  in  the  formation  of  the  germ-layers  is  very  difficult  to  determine  and 
in  spite  of  a  painstaking  study  upon  a  great  many  embryos,  I  cannot  regard  my 
observations  on  this  point  as  quite  conclusive.  As  already  shown  (figures  6  and 
13)  in  sagittal  sections  at  a  certain  period,  a  direct  continuity  is  observable  between 
what  I  have  called  the  "  prostomal  thickening  "  and  a  thin  layer  of  cells  which  evi- 
dently represents  the  gut-hypoblast.  This  continuity  is  strong  evidence  that  the 
latter  has  been  derived  by  proliferation  from  the  former.  In  the  trout  the  pros- 
tomal invagination  commences  before  the  forma- 
tion of  the  germ  ring.  In  Mursenaf  on  the  other  FIGURE  is. 
hand,  at  a  time  when  the  blastoderm  has  covered 
nearly  one-half  the  circumference  of  the  yolk, 
neither  prostomal  invagination  nor  gut-hypoblast 
are  to  be  seen,  although  the  germ-ring  is  well 

Transverse  section  passing  through  posterior 

advanced.       At  the  next    Stage  which    I    have  Sec-      eud  of  a  very  early  trout  emhryo  (somewhat 
,.          j   ,n  i  n\  ii  11,-  later  than  that  in  figure  6).     PrHy,  hypoblast 

tioned  (figure  13)  the  gut-hypoblast  is  seen  to  be    invaginated  at ,, pro;toma.» 

in  direct  continuity  with  the  invaginated  cells, 

which  agree  witli  the  former  in  showing  a  higher  staining  power  than  the  rest  of 

the  blastoderm. 

Transverse  sections  of  these  same  stages  unfortunately  do  not  show  these  condi- 
tions with  the  same  degree  of  clearness.1  The  lowermost  cells  do  not  exhibit  the  dis- 
tinct epithelial  arrangement  seen  in  longitudinal  sections.  In  fact  what  appears  in 
the  latter  as  a  continuous  ventral  layer,  extending  beneath  the  entire  embryonic 
region  of  the  blastoderm,  is  only  to  be  observed  with  distinctness  in  those  cross-sec- 
tions which  pass  through  the  extreme  posterior  end.  It  is  clearly  marked  in  several 
blastoderms  which  I  have  cut  (figure  18).  What  becomes  of  this  layer  in  the  cepha- 
lad  portion  is  not  revealed  in  transverse  sections  of  embryos  at  such  an  early  stage. 
At  a  later  period  when  the  gut-hypoblast  has  finally  become  distinctly  differentiated 
throughout  the  entire  region  of  the  embryo,  it  is  found  that  a  conspicuous  break  in 
its  continuity  occurs  along  a  considerable  extent  of  the  axial  line.  The  gut-hypo- 
blast  now  occurs  in  two  lateral  sheets,  each  sheet  being  merged  axiad  into  the  un- 
differentiated  cord  of  cells  which  form  the  "  primitive  streak  "  (figure  19). 

The  question  at  once  arises — was  the  lowermost  germ-layer,  at  the  time  of  its  first 

1  I  have  transverse  sections  of  Nolurus,  Amiurus  and  Salvelinun  embryos  during  this  period,  but  unfortunately,  none 
of  Slnrtsna? 


60 


MEMOIRS  OF  THE  NEW  YORK   ACADEMY  OP  SCIENCES 


FIGUBE  19. 


Transverse  section  through  "primitive  streak" 
region  of  a  Noturus  embryo  of  about  the  stage  rep- 
resented in  Figure  22. 


appearance,  a  single  continuous  sheet,  which  later  fused  along  the  axial  line  with 
the  overlying  cells;  or  was  it  differentiated  from  the  overlying  cell-layer,  retain- 
ing, however,  its  original  continuity  with  the  latter  along  the  axial  line  ;  or  finally, 
has  the  course  of  events  been  complicated  by  some  process  which  we  have  left  out 
of  consideration  ?  So  far,  my  study  of  sections  has  not  afforded  a  final  answer  to 

this  question.  In  longitudinal  sections,  such 
as  those  shown  in  figures  6  and  13,  I  can- 
not find  any  evidence  of  a  break  in  the  con- 
tinuity of  this  layer  across  the  median  line. 
Since,  however,  the  layer  is  not  perfectly 
distinct  at  all  points,  I  cannot  feel  sure  of 
this  fact.  As  stated  above,  transverse  sec- 
tions have  so  far  failed  to  clear  up  the 
matter. 

The  relation  of  the  gut  epithelium  to  the  notochord  is  also  an  interesting 
problem.  For  some  time  after  the  chorda  has  separated  from  the  neural  axis  above 
and  the  mesoblastic  plates  on  each  side,  there  persists  a  continuity  between  it  and 
the  gut-hypoblast.  Does  this  continuity  reveal  the  actual  method  of  chorda  forma- 
tion in  teleost  ontogeny,  or  is  the  union  a  secondary  one  ?  Also,  what  is  the  mean- 
ing of  the  suggestive  union  occurring  at  certain  points  between  the  mesoblastic 
plates  and  the  hypoblast?  (See  figure  20.)  Clearer  light  may  be  thrown  upon 
some  of  these  points  in  the  ensuing 
discussion  of  the  meaning  of  the 
"prostoma." 

Before  leaving  this  topic  it  is 
well  to  emphasize,  however,  that  a 
part,  though  at  present  an  uncertain 
part,  of  the  embryonic  hypoblast  is 
derived  from  that  collection  of  cells 
which  I  have  called  the  prostomal 
thickening.  Whether  or  not  this 
mode  of  origin  is  supplemented  by 

differentiation  from  the  overlying  "secondary  layer"  of  the  germ-ring,  I  cannot 
definitely  say. 

There  is  certainly  one  region  of  the  blastoderm  where  the  hypoblast  originates 
quite  independently  of  any  connection  with  the  prostomal  invagination,  namely, 
the  "non-embryonic  "  part  of  the  germ-ring.  Shortly  before  the  blastopore  closes, 


FIGURE  20. 


Section  passing  through  posterior  half  of  embryo  of  Noturus, 
somewhat  in  front  of  Kupffer's  Vesicle  (cam.  luc. ).  The  relations 
of  gut-hypoblast  to  mesoblast  and  chorda  are  suggestive. 


SUMNER:    KUPFFER'S   VESICLE  61 

that  part  of  the  blastoderm  forming  its  now  posterior  margin  (in  Noturus  and 
Murxnaf)  is  seen  to  be  differentiated  into  all  three  germ-layers  (see  figure  14). 
VIRCHOW  ('95)  describes  this  condition  in  the  trout  and  I  ('99,  a)  have  already  re- 
corded it  for  Noturus. 

Historical. — With  the  exception  of  the  earlier  investigators,  who  derived  the 
entoderm  from  the  periblast,  nearly  all  writers  on  fish  embryology  have  thought 
this  germ-layer  to  arise  as  a  differentiation  from  the  inflected  layer  of  the  germ- 
ring.  The  cells  of  the  latter  were  held  to  separate  sooner  or  later  into  two  layers, 
the  lower  of  which  was  the  entoderm,  the  upper  the  mesoderm.  The  only  writers, 
as  far  as  I  know,  who  have  maintained  the  existence  of  a  distinct  entoderm  rudi- 
ment are  KOWALEWSKI  (see  above),  BERENT  ('96),  and  REINHARD  ('98). 

BERENT  maintains  that  the  entoderm  arises  as  a  separate  rudiment  and  has 
figured  it  with  approximate  correctness  in  one  stage  (figure  21,  B).  But  his  inter- 
pretation of  the  process  is  certainly  wrong.  The  accompanying  figure  21,  A  from 

FIGURE  21. 


After  Berent — illustrating  his  view  of  entoderm  formation. 

BERENT  is  probably  based  upon  an  observation,  though  an  inaccurate  one,  of  the 
earlier  appearance  of  this  same  group  of  cells.  He  holds  the  condition  described 
by  H.  V.  WILSON  ('91)  for  the  sea-bass  (i.  e.,  a  uniform  differentiation  of  the  under 
surface  of  the  whole  embryonic  germ-ring)  to  be  the  more  primitive,  and  considers 
the  condition  he  finds  in  the  trout  to  be  a  derived  one.  My  objections  to  BERENT'S 
conclusions  are  two  :  first,  that  the  rapidly  developing  pelagic  egg  of  the  sea-bass 
would  be  far  more  apt  to  exhibit  a  precocious  development  of  any  part  than  the 
slowly  developing  egg  of  the  trout,  and  second,  that  the  account  offered  by  WILSON  is 
undoubtedly  incomplete.  While  I  have  never  studied  the  egg  of  the  sea-bass,  I 
have  carefully  sectioned  the  appropriate  stages  of  the  quite  similar  egg  of  Ctenola- 
brus,  and  find  that  here,  as  in  the  eggs  of  so  many  widely  different  fishes,  the  gut- 
hypoblast  is  plainly  formed  in  connection  with  a  prostomal  ingrowth.  Unlike 
KOWALEWSKI,  BERENT  has  missed  the  true  meaning  of  the  process.  REINHARD  re- 
gards the  entire  hypoblast  as  derived  by  proliferation  from  the  walls  of  Kupffer's 
Vesicle.  The  cells  of  the  latter  arise,  he  claims,  from  the  periblast. 


G2 


MEMOIRS   OF   THE   NEW  YORK   ACADEMY  OF   SCIENCES 


IV.     SIGNIFICANCE   OF  THE   PROSTOMAL   INV AGINATION. 

I  now  purpose  to  offer  an  interpretation  of  the  foregoing  phenomena  and  to 
point  out  their  relation  to  phases  in  the  development  of  other  vertebrates. 

My  theory  in  large  degree  reverts  to  that  proposed  by  KUPFFER  in  1884.  (Prac- 
tically formulated  in  1879 — see  KUPFFER,  '79.)  KUPFFER'S  observations,  already 
discussed,  led  him  to  a  novel  view  of  the  development  of  the  fish  embryo.  It 
was  his  endeavor  to  make  a  complete  comparison  between  the  conditions  found 
in  the  Teleostei  and  that  found  in  the  Amniota.  KUPFFER  was  the  first  to  point 
out  the  dorsal  invagination  in  the  reptilian  blastoderm,  and  he  considered  that 
in  this  he  had  found  the  homologue  of  the  gastrula  mouth  or  blastopore  of 


FIOUBE  22. 


FIGURE  23. 


Pr- 


Early  blastoderm  of  Noturus.     Gr,  germ- 
ring  ;  Pr,  "prostoma." 


Early  embryo  of  Notaries,  before  appearance  of 
caudal  knob.  The  bifid  caudal  end  of  the  embryo 
si  seen  to  embrace  a  thin  cellular  sheet  as  in  case 
of  Murxna  ?  (see  figure  27). 


Amphioxus.  The  yolk-filled  aperture  of  the  blastoderm  margin  had  nothing  to 
do  with  blastopore  proper.  For  this  aperture  he  invented  the  name  of  "  BLAS- 
TOTREMA."  He  considered  the  process  by  which  the  blastoderm  covered  the  yolk 
as  in  no  sense  a  process  of  gastrulation  but  as  a  process  of  blastosphere  formation, 
thinking  that  the  completed  blastosphere  would  surround  the  yolk  on  all  sides. 
KUPFFER  sought  for  and  found  a  homologue  of  the  reptilian  prostoma  in  teleosts. 
This  invagination,  he  says,  at  first  +  shaped  in  .  surface  view,  greatly  elongates 
in  a  forward  direction,  resulting  in  the  formation  of  a  longitudinal  groove  which  he 
calls  the  "  primitive  groove,"  extending  along  the  axis  of  the  embryo.  He  dif- 
fers in  his  interpretation  of  the  primitive  groove  and  streak  from  BALFOUR,  who, 
as  well  known,  considered  these  structures  to  be  homologous  with  the  seam  along 
with  the  blastoderm  edges  united  behind  the  embryo  in  the  elasmobranch  (figure 
29,  A,  Bl).  Thus,  according  to  BALFOUR  ('78  and  '81)  the  primitive  streak  is  posterior 


SUMNER:    KUPFFER'S   VESICLE  63 

to  the  neurenteric  canal,  while  KUPFFER  held  it  to  be  anterior  to  the  latter.  The 
real  representative  of  the  "  Raphe"  or  line  of  union  of  the  blastoderm  edges  of  the 
shark,  KUPFFER  found  in  the  so-called  "  Caudal  Knob"  (Randhugel)  appearing  at 
an  early  period  .at  the  posterior  end  of  the  trout  embryo.  This  comparison  was 
based  upon  the  supposition  that  the  "  prostoma,"  or  blastopore  of  the  meroblastic 
vertebrates,  was  originally  situated  upon  the  blastoderm  margin  as  in  the  shark,  and 
that  its  more  anterior  position  in  Teleosts  and  Amniota  had  been  due  to  a  removal 
from  its  primitive  situation.  It  is  not  plain,  however,  whether  or  not  KUPFFER 
regarded  this  change  of  position  as  occurring  in  the  ontogeny  of  the  teleosts. 

This  original  invagination,  occurring  immediately  in  front  of  the  caudal  knob, 
resulted  in  the  formation  of  the  much  discussed  vesicle,  which  represented  that  part 
of  the  archenteron  forming  the  allantois  of  the  amniota. 

There   seems  to    be   no   doubt   now   that  the    "  primitive              FIGURE  24. 
groove  "  seen  by  KUPFFER  in  the  trout  was  nothing  more  than 
the  medullary  furrow.     KUPFFER  apparently  made  little  use  of 
sections  and  he  does  not  give  a  single  figure  of  one  illustrating     jfcj 
this  point.     But  his  main  ideas,  namely,  that  there  occurs  in 
the  teleosts  a  dorsal  invagination  comparable  to  that  in  the  rep- 
tile, and  that  this  invagination  has  been  removed  from  a  prim-     '-^—^..^f^ ^"— ~7 

itive  marginal  position,  are  fully  borne  out  by  the  present  in- 
vestigations.    I  differ  from  KUPFFER,  however,  in  regarding  the       Not«™s  embryo  after  ap- 
pearance of    caudal  knob 
"prostoma"  as  representing  only  a  limited  part  of  the  blasto-     (<*). 

pore,  the  remainder  being  constituted  by  the  entire  blastoderm 
margin  (KUPFFER'S  "  Blastotrema").     Again  I  find  strong  evidence  that  this  detach- 
ment of  the  "prostoma"  from  the  margin  occurs  in  ontogeny  in  the  teleost  as  well 
as  in  the  elasmobranch,  a  point  left  uncertain  by  KUPFFER. 

If  such  a  process  occurs,  it  must  on  theory  take  place  some  time  before  the  ap- 
pearance of  Kupffer's  Vesicle,  since  this  represents  the  expanded  inner  end  of  the 
"  prostoma."  Figure  22  shows  the  condition  of  a  Notunw  blastoderm  at  this  period. 
The  indentation  of  the  blastoderm  margin  and  its  relation  to  the  future  axis  of  the 
embryo  recall  at  once  the  figures,  given  us  by  Duval  ('84)  of  the  early  chick  blasto- 
derm. These  will  be  referred  to  "later.  Figure  23  represents  a  somewhat  more  ad- 
vanced stage  and  demands  no  further  explanation.  Figure  24  shows  the  appear- 
ance of  an  embryo  in  which  Kupffer's  Vesicle  has  formed.  The  indented  posterior 
margin  has  now  given  place  to  a  rounded  projection,  a  condition  which  we  should 
expect  to  exist  after  the  final  union  of  the  sides  of  the  indentation,  in  other  words, 
after  the  detachment  of  the  prostoma  from  the  yolk  blastopore. 


64 


MEMOIRS  OF  THE  NEW  YORK  ACADEMY  OF  SCIENCES 


The  emarginate  condition  is  also  well  shown  in  the  transparent  living  egg  of 
Scorpsena.  It  is  true  that  figure  25  shows  a  shallow  bay  rather  than  sharp  nick, 
but  the  conspicuous  shingle-like  overlapping  of  the  cells  along  the  whole  posterior 
margin  speaks  strongly  for  a  process  of  concrescence.  This  appearance  of  the  blas- 
toderm margin  recalls  the  descriptions  of  RYDER  ('86)  for  Elacate  and  of  LOCY  ('95) 
for  Squalus,  and  it  seems  quite  possible  that  the  structures  which  were  by  those 
writers  given  a  segmental  value  find  their  true  explanation  here.  In  figure  26 
the  emarginate  condition  has  for  some  time  ceased  to  exist  and  Kupffer's  Vesicle 
has  come  into  view  at  a  considerable  distance  from  the  margin.  Behind  this  the 
caudal  knob  projects  into  the  yolk  blastopore. 

In  the  egg  of  Mursena  f  which,  as  above  described,  exhibits  the  prostoma  in  its 
least  modified  form,  there  is  also  the  strongest  evidence  of  this  view  of  its  formation. 


FIGURE  25. 


FIGURE  26. 


Pr' 


Living  egg  of  Scorpsena.  Pr,  emarginate  region  at  pos- 
terior end  (not  often  as  deeply  concave  as  in  figure).  Ar- 
rangement of  cells  on  either  side  strongly  suggests  con- 
crescence. 


Kv 


Scorpiena  embryo  after  caudal  knob  and  Kupffer's  Vesi- 
cle have  appeared  to  view. 


Figure  27  shows  a  deep  bay  extending  forward  from  the  blastopore  into  the  pos- 
terior end  of  the  embryo.  It  is  evident  from  transparent  view  that  the  yolk  is  not, 
however,  exposed  in  this  bay  as  in  the  rest  of  the  blastopore  (compare  with  condi- 
tion in  Noturus,  shown  in  figure  23).  The  section  (figure  28)  verifies  this  opin- 
ion. It  is  at  once  seen  that  at  this  point  the  invagi nation  to  form  the  hypoblast  (as 
above  discussed)  is  occurring. 

In  this  connection  it  is  significant  to  note  that*  there  seems  to  be  a  certain  rela- 
tion between  the  time  of  appearance  of  the  caudal  knob  and  the  age  at  which  Kupf- 
fer's Vesicle  is  formed.  In  the  embryo  of  the  trout,  the  caudal  knob  appears  at  a 
period  when  the  blastoderm  occupies  but  a  small  part  of  the  upper  hemisphere  of 
the  egg.  The  definitive  Kupffer's  Vesicle  is  formed  some  time  before  the  equator 
has  been  passed.  In  Noturus,  the  caudal  knob  is  not  developed  until  about  one-half 


SUMNER:   KUPFFER'S  VESICLE  65 

of  the  yolk  has  been  covered,  and  Kupffer's  Vesicle  appears  somewhat  later ;  in  Scor- 
pxna,  the  relative  time  of  formation  of  both  of  the  structures  is  still  later,  at  least 
four-fifths  of  the  yolk  being  covered  ;  while  in  Mursena  f  the  vesicle  does  not  ap- 
pear to  view  until  the  blastopore  is  nearly  closed,  and  the  caudal  end  of  the  embryo 
is  conspicuously  bifid  up  to  the  time  when  the  blastopore  is  very  small.  Of  course 
this  line  of  argument  is  open  to  the  reply  that  the  time  of  appearance  of  both  these 
structures  is  conditioned  by  the  general  rate  of  development  of  the  embryo  in  any 
particular  case  and  that  the  coincidence  stated  does  not  prove  any  necessary  relation- 
ship between  the  two. 

As  might  be  expected,  an  indentation  of  the  posterior  end  of  the  embryo 
has  been  already  noted  by  several  investigators.  AGASSIZ  and  WHITMAN  ('84)  once 
or  twice  observed  this  condition  in  living  pelagic  eggs  and  regarded  it  as  strong  evi- 
dence for  the  formation  of  the  embryo  by  concrescence.  HENNEGUY  ('88)  noted  its 

FIGURE  27.  FIGURE  28. 


The  posterior  end  of  embryo  of  Marietta?  just  prior  to        Oblique  section  of  preceding  embryo, 
closure  of  blastopore.     Yp,  yolk-plug  ;  Pr,  "  prostoma  "  ; 
X-Y,  plane  of  section  shown  in  FIGURE  28. 

existence  in  a  single  egg  and  from  this  concluded  that  concrescence  occurred  in  the 
fish  embryo  in  a  very  limited  region,  i.  e.,  enough  to  form  the  caudal  knob,  although 
not  giving  to  this  process  any  such  interpretation  as  we  have  had  under  discussion. 
M'INTOSH  and  PRINCE  ('90)  speak  of  a  "  terminal  bay "  in  certain  pelagic  eggs. 
EYCLESHYMER  ('95)  notes  that  this  indented  condition  has  been  already  observed  in 
Amiurus  by  Miss  O'GRADY,  of  Vassar.  JABLONOWSKI  ('98)  describes  the  artificial 
production  of  a  similar  condition  in  the  Salmonidse,  by  the  use  of  salt  solution. 

Reference  might  also  be  made  to  the  Mesodidymi  arid  Hemididymi  of  various 
authors,  although  I  do  not  consider  it  necessary  to  discuss  them  here. 

Thus  the  prostoma  of  the  teleost,  like  the  neurenteric  canal  of  the  shark,  repre- 
sents a  specialized  portion  of  the  blastopore  which  has  become  detached  from  the 
remainder  by  a  process  of  concrescence  or  union  of  the  blastopore  lips.  Figure  29, 
A  and  B,  illustrate  this  comparison.  It  will  be  seen  that  the  homology  suggested 


66 


MEMOIRS  OF  THE   NEW  YORK   ACADEMY  OF  SCIENCES 


by  KUPFFER  between  the  caudal  knob  (Ck)  of  the  teleost  and  line  of  fusion  of  the 
blastoderm  edges  behind  the  embryo  of  the  shark  is  in  principle  true,  though  not 
quite  exact.  The  caudal  knob  of  the  teleost  represents,  rather,  the  embryon'c  tail- 
end  of  the  shark,  enclosing  the  neurenteric  canal.  (This  is  the  view  maintained 
by  SCHWARTZ  '89,  though  I  did  not  know  it  when  the  foregoing  words  were  written. 
Concerning  KOPSCH,  see  below.)  The  posterior  line  of  fusion  (Bl)  has,  strictly  speak- 
ing, no  counterpart  in  the  teleost,  inasmuch  as  the  embryo  retains  its  connection 
with  the  blastoderm  margin. 

H.  VIRCHOW  ('95)  proposes  a  view  of  the  teleost  embryo  similar  in  some  respects 
to  those  of  KUPFFER  and  myself.  He  considers  the  caudal  knob  to  result  from  a 
process  of  folding  similar  to  that  in  the  elasmobranch.  In  the  latter,  he  says,  all 
three  of  the  germ  layers  are  folded  off  and  the  tail  projects  freely,  while  in  the  trout 
the  folding  process  affects  merely  the  ento-  and  mesoderm,  the  ectoderm  taking  no 

FIGURE  29. 


Schematic  figures  of  A,  early  elasmobranch  (after  Balfour),  and  B,  teleost  embryo  illustrating  the  author's  view  of 
the  formation  of  the  teleost  embryo.  Mg,  medullary  groove  ;  Ne,  neurenteric  canal  ;  Bl,  line  of  fusion  of  edges  of 
blastoderm  behind  the  latter  ;  Yk,  yolk. 

part  in  the  process.  This  ventral  folding  off  of  the  entoderm  results  in  the  forma- 
tion of  Kupffer's  Vesicle  which  is  thus,  in  its  origin,  like  any  other  part  of  the  gut. 
But  as  VIRCHOW  does  not  recognize  the  presence  of  the  "  prostoma,"  nor  the  part 
played  by  concrescence,  his  account  is  incomplete.  He  attributes  a  similar  view  to 
OELLACHER,  though  I  do  not  recall  the  latter's  statement.  The  views  of  KOPSCH 
and  JABLONOWSKI  will  be  considered  below. 

If  the  theory  I  have  advocated  is  correct,  it  is  evident  that  the  development  of 
the  teleost  egg  differs  far  less  from  that  of  the  other  meroblastic  vertebrate  eggs  than 
has  usually  been  held.  In  all  of  these,  it  seems  probable  that  the  originally  simple 
blastopore,  consisting  of  the  whole  exposed  surface  of  the  yolk,  has  been  separated 
by  a  process  of  concrescence  into  an  anterior,  embryonic  portion  and  a  posterior,  non- 
embryonic  portion.  For  the  bird's  egg,  the  case  has  been  convincingly  presented  by 
DUVAL  ('84).  The  primitive  streak,  although  appearing  to  originate  at  some  distance 


SUMNER  :    KUPFFER'S  VESICLE  67 

from  the  blastoderm  margin,  has  been  shown  by  him  to  arise  in  connection  with  the 
latter,  in  fact,  to  arise  from  a  portion  of  the  latter.1  In  the  egg  of  the  reptile,  the 
connection  of  the  plate  of  cells  in  which  invagination  occurs  with  the  blastoderm  has 
not  yet  been  established,  but  we  cannot  doubt  that  even  here  the  invaginate  part  has, 
in  phylogeny  at  least,  been  detached  from  a  primitive  position  on  the  margin.  An 
interesting  parallel  occurs  between  the  fate  of  the  prostomal  cavity  (KupfFer's  Vesicle) 
in  the  teleost  and  that  of  the  invaginate  cavity  in  the  reptile.  It  has  been  shown 
that  the  latter  breaks  through  at  its  inner  extremity,  thus  becoming  connected  with 
a  large  sub-germinal  cavity.  Two  regions  of  the  archenteron,  at  first  separate,  are 
thus  brought  into  union.  Now  SOBOTTA  ('98) — at  least  I  so  interpret  Sobotta's  state- 
ment— and  GREGORY  ('99)  have  described  a  union,  at  a  certain  period,  between  the 
cavity  of  KupfFer's  Vesicle  and  the  lumen  of  the  gut  in  front  of  it.  This  parallel 
was  called  to  my  attention  by  Professor  MINOT. 


A,  B  and  C.    Showing  three  stages  in  the  formation  of  the  embryo  of  the  toad-fish.     (After  Miss  Clapp. ) 

This  dichotomizing  of  the  blastopore  is,  in  the  elasmobranchs  and  the  sauropsida, 
very  evidently  due  to  the  great  relative  amount  of  the  yolk,  which  renders  the  epi- 
bolic  growth  of  the  blastoderm  a  slow  process,  thus  making  it  necessary  for  the  form 
of  the  embryo  to  be  established  long  before  the  close  of  gastrulation.  In  the  case 
of  the  teleost,  the  yolk  as  a  rule  is  far  smaller,  so  that  the  yolk  blastopore  is  able  to 
close  at  a  period  when  the  embryo  is  much  less  advanced.  In  this  group,  accord- 
ingly, we  find  the  caudad  growth  of  the  embryo  to  take  place  at  a  rate  about  equal 
to  that  of  the  blastoderm  margin.  Consequently,  although  the  folding-off  of  the  tail 
end  occurs  here,  as  in  the  shark,  resulting  in  the  detachment  of  a  portion  of  the  blasto- 
pore, the  embryo  retains  throughout  its  connection  with  the  border  of  the  blastoderm. 
That  this  is  the  true  explanation  of  the  difference  in  the  position  in  the  two  groups 
is  shown  by  certain  exceptional  teleosts  where  this  marginal  position  of  the  embryo 

1  It  is  true  that  the  experiments  of  ASSHETON  ('96)  have  not  supported  Duval's  theory.  [Since  writing  the  fore- 
going, I  have  fully  confirmed  such  of  Assheton's  results  as  go  to  prove  that  the  primitive  streak  of  the  bird  does  not 
arise  from  the  blastoderm  border  in  ontogeny.  This  in  no  way  disproves,  however,  that  it  so  arose  in  phytogeny,  and 
I  believe  that  there  still  remain  strong  reasons  for  such  a  view.— September  21,  1900.] 


68  MEMOIRS  OF  THE  NEW  YORK   ACADEMY  OF  SCIENCES 

is  lost.  In  the  toad-fish  (Batrachus)  according  to  Miss  CLAPP  ('91)  the  caudal  end 
of  the  embryo  parts  company  with  the  margin  of  the  blastoderm  at  a  relatively 
early  period  (figure  30,  A,  B,  C).  EYCLESHYMER  reports  a  similar  condition  for 
Lophius,  though  his  description  and  figures  do  not  bear  out  such  a  contention.  The 
latter  author  infers  from  certain  appearances  that  the  same  process  occurs  in  Amiurus 
as  well.  In  this,  EYCLESHYMER  is  certainly  wrong.  The  embryo  of  this  fish  in- 
variably retains  its  connection  with  the  germ-ring  until  the  complete  closure  of  the 
yolk  blastopore.  JHERING,  also,  ('88)  has  described  what  seems  to  be  a  similar 
condition  for  the  South  American  cat-fish  Arius.  The  eggs  of  Batrachus,  Lophius  and 
Anus  are  all  extraordinarily  large,  the  latter  being  as  much  as  18  mm.  in  diameter. 
Again,  CORNING  ('96)  reports  this  separation  of  the  caudal  end  of  the  embryo  from 
the  germ-ring  to  exceptionally  occur  at  a  relatively  late  period  in  the  salmon. 

It  will  be  recalled  that  Amia  was  included  among  the  forms  exhibiting  the  "pro- 
stoma,"  although  it  is  now  certain  that  the  egg  of  Amia  is  a  holoblastic  one.  How- 
ever this  may  be,  the  egg  of  this  ganoid  is  probably  secondarily  holoblastic,  for  it 
shows  other  evidences  than  the  one  considered  of  having  been  derived  from  a  mero- 
blastic  egg.  For  instance,  my  discovery  in  Amia  (SUMNER,  '00,  a)  of  a  rudimentary 
syncytium  or  "periblast"  with  typical  giant  nuclei  confirms  the  above  view  (figures 
16  and  17)  although  this  fact  is  also  open  to  the  interpretation,  as  Professor  Mi  not 
has  suggested  to  me,  of  being  anticipative  of  the  condition  found  in  the  teleost  rather 
than  derived  from  that  in  the  shark.  I  do  not,  however,  offer  the  case  of  Amia  as 
being  nearly  as  well  established  as  that  of  the  teleosts  mentioned. 


V.     CONCRESCENCE  AND  CONFLUENCE. 

Problem  Stated. — In  the  foregoing  pages  concrescence  has  been  discussed  only 
in  relation  to  that  process  by  which  the  hinder  end  of  the  embryo  becomes  folded 
off  from  the  margin  of  the  blastoderm.  It  will  be  remembered  that  BALFOUR  ('81), 
while  admitting  the  occurrence  of  concrescence  to  this  extent,  denied  to  it  any  part 
in  the  formation  of  the  embryonic  body  itself.  So  far,  I  have  affirmed  the  process 
only  to  the  degree  admitted  by  BALFOUR. 

I  cannot  go  further,  however,  without  facing  the  general  problem  of  concrescence. 
I  must  defer  to  a  subsequent  paper  a  review  of  the  endless  mass  of  literature  bearing 
upon  this  interesting  subject.  In  this  article,  I  shall  merely  point  out  that  my  conclu- 
sions are  quite  in  harmony  with  the  results  reached  by  the  two  investigators  who  have 
given  most  labor  to  the  experimental  study  of  concrescence  in  the  teleost  embryo. 


SUMNER:   KUPFFER'S  VESICLE  69 

"  CONCRESCENCE  "  as  applied  to  the  growth  of  the  embryo,  may  be  taken  in  two 
entirely  different  senses  and  a  failure  to  recognize  this  difference  may  lead  to 
much  confusion.  As  originally  conceived  by  His,1  concrescence  was  a  process  by 
which  the  lateral  portions  of  the  germ-ring  were  actually  apposed  to  one  other  be- 
hind the  embryo,  which  thus  grew  backward  pari  passu  with  their  union.  In  this 
case,  the  embryo  was  looked  upon  as  formed  by  the  coming  together  of  the  two 
halves  of  the  germ-ring  as  such,  the  successive  levels  in  the  body  of  the  former 
being  at  the  outset  represented  by  successively  distant  portions  of  the  circumference 
of  the  latter.  The  term  "  concrescence  "  may  be  extended  in  its  application,  how- 
ever, to  a  process  quite  different  from  this.  The  growth  of  the  embryo  may  still 
be  regarded  as  taking  place  at  the  expense  of  the  germ-ring,  but  merely  in  the  sense 
that  the  latter  furnishes  undifferentiated  building-material,  which  is  first  organized 
after  reaching  the  embryonic  region.  In  this  case,  the  cells  composing  the  opposite 
halves  of  the  germ-ring  are  conceived  to  undergo  a  gradual  concentration  toward  the 
axis  of  the  embryo  as  the  latter  grows  backward.  This  axial  concentration  is  part 
of  the  same  general  process  by  which  the  broad  "embryonic  shield"  gives  rise  to  the 
narrow,  but  greatly  thickened  body  of  the  definitive  embryo.  It  is  clear  that  such  a 
centripetal  movement  of  the  germ-ring  cells  would  not  necessarily  result  in  a  growth 
of  the  embryo  by  accretion  at  its  posterior  end.  On  the  contrary,  its  growth  might, 
in  this  case,  occur  by  intussusception,  the  newly  added  cells  reaching  the  embryo  at 
some  point  anterior  to  the  caudal  end.  This  second  possible  mode  of  concrescence 
I  prefer  to  call  "  CONFLUENCE." 

Turning  to  my  own  studies,  it  is  evident  that  I  have  explained  the  detachment 
of  the  prostoma  from  the  yolk  blastopore  by  a  process  of  concrescence  in  the  former 
sense  (apposition).  The  duration  and  extent  of  this  process  I  have  not  so  far  de- 
termined, but  for  many  reasons  I  feel  convinced  that  the  folding-off  of  the  hinder 
end  of  the  body  is  merely  the  last  step  in  a  process  of  concrescence  by  which  a  whole 
or  part  of  the  length  of  the  then-existing  embryo  has  been  formed.  I  am  equally 
convinced  that  after  the  detachment  of  the  prostoma  and  the  appearance  of  caudal 
knob,  concrescence  in  this  sense  ceases  entirely.  For  unless  we  believe  this  to  have 
come  to  a  close,  it  would  be  difficult  to  account  for  the  continued  presence  of  the 
projecting  caudal  knob  at  the  posterior  end.  Again,  if  there  occurred  a  union  of 
the  halves  of  the  germ-ring  behind  the  embryo,  after  the  formation  of  Kupffer's 

1  First  stated  in  print  in  Verh.  d.  Leipzigcr  naturfor.ich.  Gen.,  June  5,  1874.  In  the  same  year  appeared  "  Unsere 
KiJrperform."  After  this,  His  reiterated  the  theo  y  many  times,  his  last  utterance  on  the  subject  being  in  1891  (see 
His  '91).  His  was  in  large  measure  anticipated  by  LKUEBOULLET  ('63)  who  distinctly  affirmed  that  the  two  sides  of 
the  embryonic  body  arose  from  the  two  halves  of  the  "  bourrelet  blaslodermique,"  or  "bourrelet  embryngene,"  as  he  calls  it 
in  view  of  its  supposed  fate.  Lereboullet  did  not,  however,  describe  the  procesa  by  which  the  body  arose  from  the 
"  bourrelet." 


70  MEMOIRS  OF  THE  NEW  YORK   ACADEMY  OF  SCIENCES 

Vesicle,  there  would  be  a  rapid  increase  in  the  distance  between  the  latter  and  the 
caudal  end.  But  this,  as  HENNEGUY  was  first  to  point  out  is  untrue.  The  writer 
has  verified  HENNEGUY'S  observations,  which  were  made  upon  trout  embryos,  by 
camera  lucida  measurements  made  upon  the  living  egg  of  Scorpsena.  Whether, 
however,  there  occurs,  after  the  appearance  of  the  caudal  knob,  a  process  of  con- 
crescence in  the  second  sense  ("confluence")  is  a  question  upon  which  my  own 
observations  throw  little  light.  [See  Supplement.]  The  experiments  of  other  in- 
vestigators, as  we  shall  see,  speak  strongly  for  this  view. 

Experiments  of  Morgan  and  Kopsch. — MORGAN  ('95), l  working  upon  the  egg 
of  Fundidus,  performed  the  crucial  experiment  of  cutting  the  germ-ring  to  one  side 
of  the  embryo.  In  a  number  of  cases,  nearly  normal  embryos  developed  in  spite  of 
their  severance  from  the  hypothetical  sources  of  building  material.  He  rejects,  on 
what  seems  to  me  to  be  insufficient  grounds,  the  supposition  that  a  process  of  regen- 
eration has  taken  place  on  the  injured  side.  MORGAN'S  accounts,  it  is  important  to 
note,  mentions  two  cases  in  which  injury  to  the  germ-ring  resulted  in  a  deficiency  of 
mesoblast  on  tbe  corresponding  side  of  the  embryo.  For  this  and  other  reasons  he 
concludes  that  the  germ-ring  normally  does,  in  part  at  least,  pass  into  the  embryo 
during  growth,  but  he  also  holds  that  it  furnishes  a  relatively  small  part  of  the  sub- 
stance of  the  latter. 

The  experiments  conducted  by  KOPSCH  ('96)2  upon  the  egg  of  the  trout  differ 
from  those  of  his  predecessor  mainly  in  being  more  systematic  and  thorough.  He 
finds  that  the  effects  of  injuring  the  germ-ring  vary  with  the  position  of  the  injury 
and  the  stage  at  which  it  is  inflicted.  After  the  caudal  knob  has  appeared,  any  in- 
jury to  the  germ-ring  laterad  to  this  does  not  prevent  the  corresponding  side  of  the 
embryo  from  developing  with  a  normal  number  of  somites.  This  side  is,  however, 
less  strongly  developed,  in  point  of  quantity  of  mesoblast,  than  the  opposite  (thus 
agreeing  with  MORGAN).  Injury  to  the  embryo  during  an  early  "  embryonic  shield" 
stage,  before  a  tail-bud  has  appeared,  gives  results  varying  according  to  the  location 
of  the  injury.  If  the  latter  is  in  the  center,  no  growth  takes  place  here,  but  the 
"non-embryonic"  borders  of  the  blastoderm  continue  to  surround  the  yolk,  leaving 
the  punctured  spot,  at  the  time  of  closure,  at  the  (anterior)  end  of  a  long  slit.  If 
the  injury  is  slightly  laterad,  an  embryo  develops,  having  a  perfect  head,  but  the 
trunk  fails  to  develop  on  the  injured  side.  If  the  injury  is  still  further  laterad,  an 
embryo  results  but  not  so  strongly  developed  on  the  injured  side  (see  above). 

1 A  preliminary  account  of  these  experiments  is  to  be  found  in  the  Aunt.  Anz.,  1893.  KASTSCHKNKO,  in  1888, 
had  performed  similar  experiments  upon  the  Selachian  embryo,  his  results  leading  him  to  oppose  the  concrescence  theory. 

2KopSCH's  later  experiments  ('99)  in  producing  artificial  Hemididymi  I  shall  not  discuss,  inasmuch  as  his  results 
are  equally  well  explained  upon  the  orthodox  view  of  concrescence. 


SUMNER:    KUPFFER'S   VESICLE  71 

KOPSCH  concludes  from  these  results  that,  at  the  time  of  the  first  appearance  of 
the  embryonic  Anlage,  the  head  rudiment  (K,  figure  31,  A)  is  median,  the  cell- 
masses  (R)  destined  for  the  halves  of  the  trunk  and  the  tail  are  laterad  to  this.  The 
formation  of  the  caudal  knob  ("Knopf,"  R,  figure  31,  B)  results  from  the  union 
of  the  two  lateral  masses  behind  the  head  rudiment.  The  "  Knopf"  is  the  re- 
pository for  the  trunk  and  tail  Anlagen,  which  thus,  even  at  this  early  stage, 
come  to  lie  in  the  middle  line.  The  caudal  knob  does  not,  however,  depend  for  its 
growth  entirely  upon  a  multiplication  of  its  own  cells  but,  during  the  circumcres" 
cence  of  the  germ-ring,  receives  successive  portions  of  the  latter,  which  serves  merely 
as  so  much  undifferentiated  building  material.  A  concrescence  in  the  sense  em- 
ployed by  His,  he  says,  does  not  occur  in  the  Salmonidne.  The  process  by  which  the 
two  rudiments  (R)  came  together  KOPSCH  does  not  consider  as  concrescence,  although 
he  does  not  give  sufficient  reason  for  his  position.  He  makes  the  very  significant 

FIGURE  31. 


Diagrams  illustrating  Kopsch's  view  of  the  formation  of  the  embryo  from  the  germ-riug.     K,  head  anlage. 

R,  material  destined  to  form  the  trunk. 

remark  that  the  Knopf  "  contains  the  neurenteric  canal,"  although  not  stating  just 
what  he  means  by  this.  In  a  later  paper  ('99),  he  says  that  the  Knopf  is  "  com- 
posed of  two  symmetrical  halves  which  are  separated  from  one  another  by  the  ideal 
neurenteric  canal." 

The  above  conclusions  of  MORGAN  and  KOPSCH  are  in  no  way  inconsistent  with 
the  results  of  HENNEGUY'S  measurements.  HENNEGUY  located  the  growing  region 
of  the  embryo  between  Kupffer's  Vesicle  and  the  most  recently  formed  somite. 
This  HENNEGUY  offered  as  convincing  evidence  against  concrescence  by  apposition, 
and  in  doing  this  he  seems  to  have  struck  the  first  decisive  blow  against  His's  the- 
ory. If  concrescence  (confluence)  is  occurring  at  all,  he  says,  it  occurs  in  front  of 
Kupffer's  Vesicle.  This  supposition,  however,  he  also  rejects  for  reasons  which  I 
shall  not  here  discuss.  It  will  be  remembered  that  HENNEGUY  believed  the  caudal 
knob  (and  this  only)  to  be  formed  through  an  actual  process  of  concrescence  proper. 


72  MEMOIRS  OF   THE  NEW  YORK   ACADEMY  OF  SCIENCES 

There  is  no  evidence,  however,  that  HENNEGUY  attributed  any  such  significance  to 
this  last  phenomena  as  has  been  done  by  KOPSCH  and  myself. 

JABLONOWSKI  ('98)  offers  a  view  based  largely  upon  that  of  KOPSCH,  though  not 
identical  with  it.  He  regards  the  first  formed  section  of  the  embryo  as  resulting 
from  an  "  excentrischer  Zusammenziehung  "  of  the  blastopore  lips,  comparable  to 
that  described  for  Amphioxus  by  HATSCHEK.  After  the  definite  establishment 
of  the  embryonic  body  (he  seems  to  have  in  mind  the  appearance  of  the  caudal 
knob)  growth  occurs  "through  multiplication  of  material  situated  in  the  Endwulst." 
The  latter  represents  only  the  anterior  (dorsal)  wall  of  the  neurenteric  canal,  which 
is  thus,  properly  speaking,  an  "incisura  neurenterica"  (His)  like  that  of  the  early 
elasmobranch.  In  favor  of  this  view  he  cites  the  artificially  produced  bifid  condi- 
tion above  described.  JABLONOWSKI,  accordingly,  recognizes  no  detachment  of  the 
neurenteric  canal  from  the  rest  of  blastopore.  Neither  JABLONOWSKI  nor  KOPSCH 
hint  at  any  relation  between  neurenteric  canal  and  Kupffer's  Vesicle. 

Conclusions. — From  the  previous  discusion,  it  is  evident  that  I  have  been  led, 
on  purely  morphological  grounds,  to  a  view  of  the  formation  of  the  fish  embryo  in 
full  accord  with  the  results  of  the  latest  work  in  the  experimental  field.  The  neur- 
enteric canal  I  have  shown,  moreover,  to  be  much  more  than  an  "ideal"  structure, 
it  having,  in  some  cases  at  least,  an  open  lumen,  and  being  in  others  represented 
by  a  solid  ingrowth  of  cells.  Of  course,  such  a  neurenteric  canal  as  occurs  in  Am- 
phioxus is  impossible  in  any  teleost,  owing  to  the  solid  condition  of  the  neural  axis. 

That  the  process  cf  concrescence,  which  leads  to  the  formation  of  the  neurenteric 
canal,  was  previously  instrumental  in  the  construction  of  the  embryonic  body  an- 
terior to  it  seems  to  be  proven  by  KOPSCH'S  experiments,  although  he  rejects  the 
word  "concrescence"  in  this  connection.  He  admits,  however,  an  apposition  of  the 
two  laterally  situated  halves,  which  is  all  that  is  necessary  for  the  present  discussion. 

The  long-continued  emarginate  condition  at  the  caudal  end  of  certain  embryos 
(see  above)  leads  me  to  the  belief  that  the  process  of  concrescence  is  one  of  con- 
siderable duration,  and  the  fusion  of  the  germ-layers  along  the  embryonic  axis 
("primitive  streak")  in  front  of  this  point,  gives  further  evidence  of  such  a  process. 
(JABLONOWSKI  also  regards  this  region  as  due  to  "Nahtbildung.")  That  concrescence 
(apposition)  ceases,  however,  with  the  formation  of  the  neurentoric  canal  is  certain. 
That  it  is  thereafter  replaced  by  a  process  of  confluence  seems  proven  by  the  experi- 
ments of  both  Morgan  and  Kopsch.  [Also  by  my  own. — See  Supplement.] 


SUMMER  :   KUPFFER'S   VESICLE  73 


VI.     FURTHER   MORPHOLOGICAL  CONSIDERATIONS. 

The  generally  accepted  view  that  Kupffer's  Vesicle  represents  a  certain  part  of  the 
archenteron  seems  to  me  to  be  true  beyond  doubt.  How  much  of  the  gastrula  cav- 
ity is  represented  by  this  structure  is  less  obvious.  It  has  been  variously  inter- 
preted as  the  allantois,  as  part  or  whole  of  the  post-anal-gut,  or  as  the  latter  plus  the 
neurenteric  canal.  The  case  of  Murasna  f  seems  to  show  that  the  neurenteric  canal 
is  not  included  in  the  vesicle  proper,  but  that  the  latter  forms  the  dilated  inner  end 
of  the  imagination  which  gives  rise  to  both.  The  neurenteric  canal,  in  most  teleosts, 
is  represented  by  a  solid  ingrowth  as  maintained  by  KOWALEWSKI.  At  the  inner 
end  of  this,  the  cavity  of  the  vesicle  forms  secondarily. 

In  many  fishes,  the  post-anal  portion  of  the  gut  FIGURE  32. 

(Kupffer's  Vesicle)  possesses  from  the  first,  as  we 
have  seen,  a  ventral  as  well  as  a  dorsal  wall.  In 
the  more  anterior  portion,  or  gut  proper,  the  lumen 
is  formed  by  a  real  or  virtual  upfolding  of  a  hori- 
zontal sheet  of  cells,  the  axial  portion  of  which  rep- 
resents the  dorsal  wall  of  the  gut,  the  lateral  por- 

Sagittal  section  showing  late  Kupffer's 

tions  representing  the  ventral.      We   should   thus  Vesicle  in 


expect  the  gut-hypoblast  to  be  continued  into  the 

dorsal,  rather  than  the  ventral  wall  of  Kupffer's  Vesicle.  This  relation  is  impossible 
to  determine  at  an  early  period,  but  figure  32  representing  a  late  stage  of  the  vesicle 
in  the  trout  embryo,  exhibits  the  expected  condition. 

The  structure  of  the  fully  formed  Kupffer's  Vesicle  and  adjacent  parts  have  been 
so  often  carefully  described  that  they  need  not  be  discussed  here  except  in  connec- 
tion, with  certain  differences,  already  mentioned,  in  the  form  which  it  assumes  in 
various  types  of  fishes.  Two  different  types  of  Kupffer's  Vesicle  have  been  de- 
scribed above,  one  with  no  cellular  floor,  the  other  from  the  first  bounded  on  all 
sides  by  cells.  That  these  two  types  exist  there  can  no  longer  be  any  doubt.  Ac- 
cording to  the  view  maintained  in  this  paper  as  to  the  significance  of  this  structure, 
it  is  obvious  that  I  must  regard  the  second  type  as  the  more  primitive.  The  forms 
in  which  the  cellular  lower  wall  has  been  described  as  wanting  are,  as  far  as  I  know, 
all  rapidly  developing  pelagic  eggs,  in  which  many  developmental  processes  are 
modified  by  abridgement.  On  the  other  hand  the  more  slowly  developing  cat-fish, 
trout  and  salmon,  in  which  there  is  reason  to  believe  that  the  type  of  development 
is  less  modified,  display  a  vesicle  with  a  complete  cellular  boundary.  An  exception 


74  MEMOIRS  OF  THE  NEW  YORK  ACADEMY  OF  SCIENCES 

to  such  a  rule,  however,  is  found  in  the  case  of  Mursena  ?  a  form  having  a  rapidly 
developing  pelagic  egg,  for  this  fish  exhibits,  in  the  formation  of  its  vesicle,  the 
hypothetical  primitive  condition  more  clearly  than  any  other  tcleost  that  has  been 
carefully  described. 

I  have  observed  both  in  Mursena  ?  and  in  the  trout  an  incompleteness  of  the 
lower  wall  of  the  vesicle  at  one  period.  The  cells  forming  the  floor  of  the  vesicle 
are  embedded  in  the  underlying  periblast  (figures  13  and  14,  A)  and  are  not  at 
all  points  in  contact  with  one  another.  This  fact,  and  the  presence  of  free  cells  in 
the  periblast  in  this  neighborhood,  might  lead  to  the  suspicion  that  the  lower  wall 
of  the  vesicle  is  formed  by  cells  derived  from  the  syncytium.  In  fact,  this  is  a 
conclusion  adopted  by  REINHARDT  ('98).  I  do  not  find  any  evidence  that  these  free 
cells  are  formed  out  of  the  periblast  proper.  They  are  present  from  a  very  early 
period  in  the  development  of  Salvelinus,  and  occur  beneath  the  whole  blastoderm, 
but  especially  at  the  posterior  end.  It  seems  probable  that  their  differentiation  as 
cells  dates  back  to  the  segmentation  period.  If  so,  they  are  to  be  regarded  merely 
as  detached  segmentation  spheres  which  have  lost  all  connection  with  the  blasto- 
derm. They  are  surrounded  by  distinct  cell-walls  and  generally  contain  normal 
nuclei.  Whether  such  free  cells  play  any  part  in  the  building  of  Kupffer's  Vesicle 
in  Salvelinus  or  Mursena  f  I  cannot  say  definitely.  In  Amiurus  and  Noturus  such  free 
cells  are  of  very  rare  occurrence.  I  have  observed  them  only  once  or  twice  in  all  the 
Amiurus  eggs  examined,  and  do  not  recall  having  seen  any  in  the  eggs  of  Noturus. 
OELLACHER  ('72)  was  probably  the  first  to  describe  this  conditional  though  he  un- 
doubtedly made  no  distinction  between  these  embedded  cells  and  the  periblast  nuclei. 

Such  an  incompleteness  in  the  ventral  wall  may  be  looked  upon  as  a  condition 
transitional  between  the  two  types  of  vesicle  described.  SOBOTTA  ('98)  has  already  of- 
fered as  a  transitional  form  the  case  of  the  rainbow  trout,  which  exhibits  a  complete, 
though  extremely  thin,  lower  wall.  That  such  cases  as  I  have  described  may  have, 
however,  some  other  morphological  significance  is  suggested  by  the  occurrence  of  a 
like  condition  in  Amia.  Here  I  find,  in  both  transverse  and  longitudinal  sections 
that  a  gap  in  the  cellular  floor  of  the  vesicle  occurs  along  the  median  line,  the  floor 
being  completed  by  the  syncytium  (figure  17). 


VII.     YOLK  VESICLES. 

In  certain  fishes,  there  exists,  in  addition  to  Kupffer's  Vesicle,  a  second  vesicle 
lying  in  the  yolk  beneath  the  floor  of  the  former.     This  structure  is  well  shown  in 


SUMNER:    KUPFFER'S  VESICLE 


75 


the  egg  of  the  "  Stone  Cat "  (Notu.rus)  although  entirely  lacking  in  the  closely  re- 
lated Amiurus.  It  appears  a  little  earlier  than  Kupffer's  Vesicle  and  attains  a 
somewhat  greater  size  (see  figure  34).  This  "  yolk  vesicle  "  is  surrounded  by  a  com- 
plete wall  of  periblast,  except  on  the  upper  side,  where  it  is  bounded  directly  by 
the  cells  of  the  embryo.  There  is  at  no  time  any  connection  between  the  two. 

EIGENMANN  ('92)  describes  in  the  case  of  Cymatogasler  a  single  large  vesicle  lying 
partly  in  the  yolk  and  partly  in  the  embryo.  This  latter  subdivides  into  three  por- 
tions :  a  lower  one,  which  he  calls  the  "yolk  vesicle"  ;  an  intermediate  portion, 
which  he  homologizes  with  the  post-anal-gut,  and  an  upper  cavity,  which  he  con- 
siders to  be  the  equivalent  of  the  neurenteric  canal.  KINGSLEY  and  CONN  ('83)  orig- 
inally described  Kupffer's  Vesicle  in  Ctcnolabras  as  arising  by  the  fusion  of  a  mass 


FIGURE  33. 


FIGURE  34. 


Kv 


Section  through  posterior  end  of  same  embryo  as  that 
in  figure  20  (camera  lucida).  Kupffer's  Vesicle  (Kv)  is 
beginning  to  make  its  appearance  aa  a  group  of  small 
vesicles. 


Transverse  section  through  embryo  of  Noturus,  showing 
fully  developed  Kupffer's  Vesicle  and  yolk  vesicle.  A 
layer  of  pavement  cells,  continuous  with  the  gut-hypo- 
blast,  is  here  seen  to  underly  the  columnar  epithelium 
forming  the  lower  wall  of  Kupffer's  Vesicle.  This 
pavement  layer  has  probably  reached  its  present  position 
by  growing  in  from  the  sides,  as  it  is  not  present  in  an 
earlier  stage  (figure  33). 


of  vacuoles  in  the  yolk,  and^this  account  has  been  confirmed  by  several  subsequent 
workers  on  pelagic  eggs  (e.  g.,  AGASSIZ  and  WHITMAN,  see  p.  52,  ante).  The  dorsal 
cellular  wall  of  the  vesicle  becomes  differentiated  above  this  resulting  single  vacuole. 
HENNEGUY  ('88)  states  that  there  frequently  occurs  beneath  the  posterior  end  of  the 
trout  embryo  a.  vesicle  in  the  yolk.  In  the  case  of  Salvelinus  the  whole  periblast  is 
much  vacuolated,  but  in  some  specimens  I  have  found  a  particularly  large  vacuole 
lying  in  the  appropriate  position.  AGASSIZ  and  WHITMAN  have  described  certain 
"secondary  caudal  vesicles"  probably  of  a  similar  nature.  M'!NTOSH  and  PRINCE 
('90)  speak  of  a  "multiplicity  of  vesicles"  in  the  gurnard  and  some  other  fishes. 
EYCLESHYMER  ('95)  describes  two  such  accessory  vesicles  in  Lophius,  one  of  which 
communicates  at  one  period  with  Kupffer's  Vesicle. 


76  MEMOIRS  OF  THE  NEW  YORK   ACADEMY  OF  SCIENCES 

I  am  convinced,  from  the  mode  of  formation  of  Kupffer's  Vesicle,  that  it  has  no 
morphological  relation  to  these  lower  cavities  in  the  periblast.  In  such  cases  as 
those  of  Ctenolabrm  the  connection  is  doubtless  a  secondary  one.  But  there  prob- 
ably exists,  as  I  maintain  below,  a  physiological  connection  between  the  two. 


VIII.     THE   FUNCTION   OF   KUPFFER'S   VESICLE. 

The  .preceding  pages  have  been  largely  concerned  with  a  morphological  interpre- 
tation of  the  embryonic  structure  known  as  Kupffer's  Vesicle.  It  is  obvious  that 
this  morphological  interpretation  in  no  way  accounts  for  the  dimensions  attained  by 
the  vesicle  during  development.  Why  should  the  lumen  of  this  quite  transitory 
post-anal-gut  reach  such  a  relatively  enormous  size  at  a  time  when,  in  the  remainder 
of  the  gut,  no  lumen  has  appeared?  Kupffer's  Vesicle  must  be  regarded  as  an  em- 
bryonic organ  having  some  definite  part  to  play  in  the  economy  of  the  growing  em- 
bryo. The  measurements  made  by  Henneguy  located  the  region  of  growth  in  the 
unsegmentated  part  of  the  embryo  lying  between  Kupffer's  Vesicle  and  the  last 
formed  somite.  Here,  then,  metabolism  is  most  active,  and  the  material  needed  for 
growth  ought  to  be  the  most  abundant.  It  is  now  a  generally  accepted  fact  that  the 
periblast  with  its  giant  nuclei  play  a  leading  role  in  the  assimilation  of  the  yolk. 
Passing  upward  from  the  deeper  layers  of  the  yolk,  we  find  that  the  yolk  spheres 
become  successively  smaller,  while  in  the  periblast  syncytium  they  are  reduced  to 
minute  granules.  Finally,  there  seems  to  occur  a  thin  fluid  layer  between  the  peri- 
blast and  the  cells  of  the  embryo  proper.  I  have  already  noted  the  occurrence  of  a 
large  vesicle  in  the  yolk  beneath  the  growing  region  of  the  embryo  in  certain  fishes. 
Around  this  vesicle  the  periblast  and  its  contained  nuclei  are  especially  abundant, 
and  within  its  interior  there  is  to  be  seen  in  sections  a  fine  coagulum,  reticulate  in 
appearance,  which  seems  to  be  of  an  albuminous  nature.  It  has  for  some  time  been 
my  view  (SUMNER,  '99,  a),  that  this  vesicle  contains  a  more  fluid  yolk,  partially 
assimilated  through  the  activity  of  the  periblast,  and  intended  for  the  nourishment 
of  the  growing  embryo.  I  have,  also  expressed  the  view  ('99,  b)  that  Kupffer's 
Vesicle  itself  represents  an  embryonic  digestive  organ  (more  properly  an  organ  of 
absorption).  Its  relation  to  the  yolk  vesicle  has  already  been  dwelt  upon.  Within 
it,  moreover,  occurs  a  coagulum  which  is  similar  to  that  found  in  the  other. 
SOBOTTA  ('98)  has  commented  upon  the  fact  that  Kupffer's  Vesicle  contains  a  fluid 
having  a  refractive  index  higher  than  that  of  water.  I  find  in  the  case  of  Scorpsena, 
that  this  is  noticeably  true  at  an  advanced  stage  in  the  development  of  the  vesicle, 


SUMNER:    KUPFFER'S   VESICLE  77 

when  the   outlines  of  the  chorda,  seen  through  the  contents  of  the  former,  are 
considerably  distorted,  this  fluid  mass  serving  as  a  bi-convex  lens. 

Microchemical  tests  as  to  the  contents  of  the  vesicle  gave  only  negative  results. 
I  subjected  the  eggs  of.  Mtirasnaf  and  Scorpsena  to  the  reagents  employed  by  LE 
DANTEC  ('90)  and  Miss  GREENWOOD  ('94)  for  the  detection  of  acid  in  the  vacuoles 
of  protozoa.  None  of  these  were  found  applicable  to  fish  eggs,  as  they  either  killed 
the  embryo  or  failed  to  stain  it;  but  I  also  used  Bismarck  Brown.  This  stain,  when 
neutral,  shows  a  very  characteristic  reaction  in  the  presence  of  acids.  But  no  appre- 
ciable reaction  was  exhibited  by  the  contents  of  Kupffer's  Vesicle. 


IX.     RECAPITULATION. 

1. — The  hypoblast  arises  in  connection  with  an  invagination  of  the  superficial 
layer  ("Deckschicht")  occurring  on  the  posterior  border  of  the  blastoderm.  This 
invagination  may  be  an  open  one  ("  Munena  "  possibly  some  others)  or  it  may  be  a 
solid  ingrowth  of  cells  (Amiurus,  Notwrus,  Salvelinus,  Fandulus,  Ctenolabrus.  A 
similar  condition  was  found  in  Amia. 

2. — This  invagination  is  the  "  prostoma  "  of  KUPFFER,  whose  descriptions  and 
theoretical  conclusions  upon  this  subject  are  in  the  main  correct. 

3. — Kupffer's  Vesicle  arises  from  the  expanded  inner  end  of  this  invagination, 
when  it  is  an  open  one ;  it  is  secondarily  formed  in  the  invaginated  mass  of  cells, 
when  solid. 

4. — Kupffer's  Vesicle,  as  is  usually  stated,  represents  the  post-anal-gut,  the  neur- 
enteric  canal  being  represented  by  the  open  duct  leading  from  the  vesicle  to  the 
exterior  in  "  Murxna  "  by  the  solid  ingrowth  in  the  other  forms  named. 

5. — A  process  occurs  in  the  teleosts  exactly  similar  to  that  folding  off  of  the  tail 
end  of  the  embryo  which  results  in  the  formation  of  the  neurenteric  canal  of  the 
elasmobranchs.  The  main  difference  between  the  two  cases  is  that  the  teleost  embryo 
continues  to  grow  backward  at  an  equal  pace  with  the  blastoderm  margin,  while  in 
the  elasmobranch,  the  embryo,  owing  to  its  relatively  slower  growth,  is  left  behind, 
thus  losing  its  continuity  with  the  border  of  the  blastoderm. 

6. — I  have  adduced  evidence  of  a  purely  morphological  character  for  a  view  of 
concrescence  which  is  supported  by  the  most  recent  experimental  work.  This  is, 
briefly,  that  true  concrescence  (apposition)  occurs  at  an  early  period  in  embryo  for- 
mation. It  ceases  with  the  appearance  of  the  caudal  knob,  which  arises  as  a  result 
of  the  above-mentioned  folding-off  of  the  neurenteric  canal.  No  true  concrescence 


78  MEMOIRS  OF  THE  NEW  YORK   ACADEMY  OF  SCIENCES 

can  occur  after  this  event,  though  it  is  probable  from  the  experiments  of  MORGAN  and 
KOPSCH,  [See  also  Supplement]  that  a  modification  of  the  process,  which  I  have 
termed  "  CONFLUENCE,"  continues  till  the  closure  of  the  blastopore. 

7. — A  second  vesicle,  lying  in  the  yolk  below  the  embryo,  is  present  in  Noturus 
and  some  other  forms. 

8. — Kupffer's  Vesicle  has  an  important  function  in  embryonic  life.  Its  position 
and  some  other  facts  suggest  that  it  plays  the  part  of  a  transitory  digestive  (absorbent) 
organ. 

DEPARTMENT  OF  NATURAL  HISTOHY,  COLLEGE  OF  THE  CITY  OF  NEW  YORK,  April  14,  1900. 


X.     NOTE   ON   METHODS. 

As  the  result  of  considerable  experimenting  upon  the  fixing  of  teleost  eggs,  I 
have  settled  upon  two  methods  which  I  now  use  almost  exclusively.  One  of  these 
is  treatment  with  ZENKER'S  Fluid.  This  reagent  gives  very  good  results  with  the 
eggs  of  Noturus  and  Amiurus,  but  I  have  found  it  to  be  far  less  satisfactory  for  fixing 
the  eggs  of  the  trout  or  those  of  pelagic  fishes.  The  second  method,  which  I  have 
found  applicable  to  all  the  eggs  I  have  studied,  consists  in  a  brief  fixation  in  subli- 
mate acetic  (10^  acetic)  followed  by  preservation  in  formalin.  The  eggs  are  allowed 
to  remain  in  the  fixing  fluid  till  the  blastoderm  or  embryo  becomes  whitened,  one 
minute  being  usually  sufficient.  After  hasty  rinsing  in  water,  they  are  transferred 
to  10^>  formalin.  This  method,  in  addition  to  securing  good  histological  fixation, 
has  the  advantage  of  not  hardening  the  yolk  and  of  preserving  the  natural  appear- 
ance of  the  egg  far  better  than  any  other  treatment  which  I  know  of.  This  method, 
Doctor  STRONG  tells  me,  originated  with  Doctor  C.  M.  CHILD. 

The  eggs  of  Amia  (kindly  furnished  me  by  Professor  DEAN)  were  preserved  by 
the  late  Doctor  ARNOLD  GRAF.  Those  which  I  sectioned  had  been  fixed  in  ZENKER'S 
Fluid  or  in  GRAF'S  Chrom-oxalic  mixture.  (See  New  York  State  Hospitals  Bulletin, 
Vol.  II,  1897.)  Both  gave  satisfactory  results. 

The  teleost  material  was  stained  according  to  HAIDENHAIN'S  "Iron  hsematoxylin " 
method.  Occasionally  I  used  an  anilin  counterstain,  though  this  was  of  no  real  ad- 
vantage. For  the  sections  of  Amia  I  employed  both  the  "  Iron  hsematoxylin  "and 
DELAFIELD'S  hsematoxylin.  The  latter  was  far  preferable  for  these  eggs. 


SUMNER:   KUPFFER'S   VESICLE  79 

XI.     SUPPLEMENT. 

Since  writing  the  foregoing  pages,  I  have  had  an  opportunity  of  putting  to  ex- 
perimental test  certain  of  the  views  therein  maintained.  At  Naples,  during  the 
past  July,  I  carried  on  experiments  with  a  view  to  determining  the  manner  of  for- 
mation of  the  embryonic  body  in  Exocoetus  sp.  My  results  will  shortly  be  pub- 
lished. I  will,  however,  briefly  record  the  confirmation  of  two  of  the  conclusions 
maintained  above. 

First,  that  the  germ-ring  passes,  in  large  part  at  least,  into  the  embryo.  Proof : 
— Glass  needles  were  inserted  into  the  eggs,  piercing  the  germ-ring  far  laterad  to  the 
caudal  end  of  the  embryo  during  an  early  stage.  At  a  late  period,  the  point  of  in- 
sertion of  the  needle  was,  in  certain  instances,  found  to  be  close  beside  the  caudal 
end  of  the  embryo.  In  these  cases  the  latter  was  conspicuously  bent  as  if  the  pos- 
terior part  had  been  drawn  towards  the  needle.  One  can  only  conclude  that  the 
segment  of  the  germ-ring  which  lay  between  the  needle  and  the  embryo  had  passed 
into  the  latter,  but  the  germ-ring  being  held  fast  on  one  side,  the  embryonic  body 
itself  was  drawn  in  that  direction. 

Second,  that,  at  least  after  a  certain  period,  there  occurs  a  process  of  confluence, 
rather  than  one  of  concrescence.  Proof: — In  cases  where  a  needle  was  inserted  at 
the  mid-caudal  point  of  the  early  embryo,  the  embryo  none  the  less  continued  to 
grow,  but  necessarily  in  a  forward  instead  of  a  backward  direction,  while  the  blasto- 
pore  continued  to  close  in  a  seemingly  normal  manner.  Indeed  there  was  nothing 
to  show  that  the  usual  concentric  growth  of  the  blastoderm  had  been  disturbed. 
The  only  possible  inference  is  that  the  germ-ring  material  entered  at  a  point  anterior 
to  the  needle  causing  the  embryo  to  elongate  in  the  only  direction  in  which  it  was 

free  to  move. 

FRANCIS  B.  SUMNER. 

C.  C.  N.  Y.— Sept.  21,  1900. 


80  MEMOIRS  OF  THE  NEW  YORK   ACADEMY  OF  SCIENCES 


BIBLIOGRAPHY. 

This  table  includes  only  those  papers  referred  to  in  the  present  article  and  lays 
no  claim  to  completeness.  The  papers  of  Henneguy  ('88),  Mclntosh  and  Prince 
('90)  and  Berent  ('96)  contain  lists  of  papers  bearing  on  early  teleost  development, 
and  Morgan  ('95)  and  Kopsch  ('99)  give  the  literature  of  concrescence.  Kopsch 
('00)  gives  a  very  complete  bibliography  of  KupfFer's  Vesicle.  (This  last  appeared 
after  the  present  memoir  had  gone  to  press.) 

Agassiz,  A.,  and  Whitman,  C.  0. 

'84.          On  the  Development  of  some  Pelagic  Fish  Eggs.     Preliminary  notice. 
Proc.  Amer.  Acad.  Arts  and  Sciences,  Vol.  XX,  pp.  23—75,  pi.  I. 

Assheton,  R. 

'96.          An  Experimental  Examination  into  the  Growth  of  the  Blastoderm  of  the  Chick. 
Proc.  Roy.  Soc.  London,  Vol.  LX,  pp.  349-356. 

Balfour,  F.  M. 

'78.          A  Monograph  on  the  Development  of  Elasmobranch  Fishes.     London,  1878. 

Balfour,  F.  M. 

'81.         Comparative  Embryology.     London,  1881. 

Berent,  W. 

'96.         Zur  Kenntniss  der  Parablastes  und  der  Keimbliitterdifferenzierung  im  Ei  der  Knoch- 

enfische. 
Jenaische  Zeitscltrift,  Bd.  30,  pp.  291-349,  Taf.  XVI-XVIII. 

Clapp,  Cornelia  M. 

'91.          Some  Points  in  the  Development  of  the  Toad  Fish  (Hatrachus  tau). 
Journ.  Morph.,  Vol.  V,  pp.  494-501. 

Corning,  H.  K. 

'96.          Merocyten  und  Umwachsungsrand  bei  Teleostiern. 

Festschrift  /.  Carl  Gegenbaur,  Bd.  2,  pp.  103-132. 
Dean,  B. 

'95.         The  Early  Development  of  Gar,  Pike  and  Sturgeon. 

Journ.  Morph.,  Vol.  XI,  pp.  1-63,  pi.  I-IV. 
Dean.'B. 

'95.         Fishes,  Living  and  Fossil.     New  York,  Macmillan  Co. 

Dean,  B. 

'96.          The  Early  Development  of  Amia. 

Q.  J.  Micr.  Sci.,  Vol.  38,  pp.  413-445,  pi.  XXX-XXXII. 

Duval,  M. 

'84.         De  la  Formation  du  Blastoderme  dans  1'Oeuf  d'Oiseau. 

Ann.  des  Sci.  not.,  Ser.  6,  Tome  XVIII,  pp.  1-208,  pi.  I-V. 


SUMNER  :   KUPFFER'S  VESICLE  81 

Eigenmann,  C.  H. 

'94.          On  the  Viviparous  Fishes  of  the  Pacific  Coast  of  North  America. 

Bull,  of  U.  S.  Fish  Com.  for  1892,  pp.  381-478,  pi.  XCII-CXVIII. 

Eycleshymer,  A.  0. 

'95.          The  early  Development  of  Amblystoma,  with  Observations  on  some  other  Vertebrates. 
Journ.  Morph.,  Vol.  X,  pp.  343-419,  pi.  XVIII-XXII. 

Gbtte,  A. 

'73.          Beitriige  zur  Entwickelungschichte  der  Wirbelthiere.     I,  Der  Keim  des  Forelleneies. 
Arch.  f.  mikr.  Anat.,  Bd.  IX,  pp.  679-709,  Taf.  XXVII. 

Greenwood,  (Miss)  M.  and  Saunders,  E.  R. 

'94.          On  the  Role  of  Acid  in  Protozoan  Digestion. 

Journ.  ofPhys.,  Vol.  XVI,  pp.  441-467,  1  pi. 

Gregory,  E. 

'99.         Die  Kupffer'sche  Blase  bei  der  Forelle  (Trutta  fario). 

Festschrift  zum  siebenzigsten  Geburtstag  von  Karl  von  Kupffer,  pp.  711—715,  Taf. 

LX,  LX1. 
Henneguy,  F. 

'88.          Becherches  sur  le  Developpement  des  Poissons  ossenx.     Embryogenie  de  la  Truite. 
Journ.  de  I' Anat.  et  de  Physiol.,  1888,  pp.  413-502  and  525-617,  pi.  XVIII- 
XXI. 

His,  W. 

'74.         Unsere  Korperform. 

Leipzig,  1874,  pp.  186-191. 

His,  W. 

'91.         Zur  Frage  der  Langsverwachsung  von  Wirbelthierembryonen. 
Verh.  d.  anat.  Ges.,  1891,  pp.  70-83. 

Jablonowski. 

'98.         Ueber  einige  Vorgiinge  in  der  Entwickelung  des  Salmonidenembryos,  nebst  Bemer- 
kungen  iiber  ihre  Bedeutung  fiir  die  Beurteilung  der  Bildung  des  Wirbeltierkorpers. 
Anat.  Anz.,  Jahrg.  14,  pp.  532—551. 

Jhering,  H.  von. 

'88.         Ueber  Brutpflege  und  Entwickelung  des  Bagre. 
Biolog.  Centr.,  Bd.  VIII,  pp.  268-271. 

Kingsley,  J.  S.,  and  Conn,  H.  W. 

'83.         Some  Observations  on  the  Embryology  of  the  Teleosts. 

Memoirs  Bost.  Soc.  Nat.  Hist.,  Vol.  Ill,  pp.  183-212,  pi.  XIV-XVJ. 

Kopsch,  F. 

'96.          Experimented  Untersuchungen  iiber  den  Keimhautrand  der  Salmoniden. 
Verh.  d.  anat.  Ges.,  1896,  pp.  113-127. 

Kopsch,  F. 

'99.          Die  Organisation  der  Hemididymi  und  Anadidymi  der  Knochenfische. 
Internat.  Monatschr.  f.  Anat.  u.  Phys.,  1899. 


82  MEMOIRS  OF  THE  NEW  YORK   ACADEMY  OF  SCIENCES 

Kopsch,  F. 

'00.         Homologie  und  Phylogenetische  Bedeutung  der  Kupffer'schen  Blase. 
Anat.  Anz.,  Bd.  XVII,  pp.  497-509. 

Kowalewski,  M.  von. 

'85.          Ueber  Furchung  und  Keimblatteranlage  der  Toleostier. 

Sitzungsber.  d.  phys.-med.  Soc.  zu  Erlangen,  Heft  18,  pp.  1-6. 

Kowalewski,  M.  von. 

'86a.        Ueber  die  ersten  Entwickhingsprocesse  der  Knochenfische. 
Zeitschr.f.  wiss.  ZooL,  Bd.  43,  pp.  434-480,  pi.  XVII. 

Kowalewski,  M.  von. 

'86b.       Die  Gastrulation  und  die  sogen.     Allantois  bei  den  Teleostiern. 

Sitzungsber.  d.  phys.-med.  Soc.  u.  Erlanrjen,  Heft  18,  pp.  31—36,  Taf.  I. 

Kupfler,  C.  von. 

'66.          Untersuchungen  iiber  die  Entwicklungen  des  Harn-  und  Geschlechtssystems.    (Second 

part.) 
Arch.f.  mikr.  Anat.,  bd.  II.,  pp.  473-489,  Taf.  XXIV. 

Kupffer,  C.  von. 

'79.          Die  Enstehung  der  Allantois  und  die  Gastrula  der  Wirbelthiere. 
ZooL  Anz.,  1879,  pp.  520-522,  593-597,  612-617. 

Kupffer,  C.  von. 

'84.          Die  Gastrulation  an  den  meroblastischen  Eiern  der  Wirbelthiere  und  die  Bedeutung 

des  Primitifstreifs,  III. 
Arch.f.  Anat.  u.  Phys.  (Anat.  Abth.\  1884,  pp.  1-40,  Taf.  I,  II. 

Le  Dantec,  F. 

'90.          Recherches  sur  la  Digestion  intracelhilaires  chez  les  Protozoaires. 
Ann.  de  Vlnstitut  Pasteur,  1890,  p.  776. 

Lereboullet,  M. 

'63.          Recherches  sur  les  Monstruosites  du  Brochet. 

Ann.  des  Sci.  nat.,  4  Serie,  Tome  XX,  pp.  177-271,  pi.  2,  3. 

Locy,  W.  A. 

'95.         Contribution  to  the  Structure  and  Development  of  the  Vertebrate  Head. 
Journ.  Morph.,  Vol.  XI,  pp.  497-594,  pi.  XXVI-XXX. 

M'Intosh,  W.  C.,  and  Prince,  E.  E. 

'90.         On  the  Development  and  Life  History  of  the  Teleostean  Food-  and  other  Fishes- 
Trans.  Roy.  Soc.  Edinb.,  Vol.  XXXV,  pp.  665-946,  pi.  I-XXVIII. 

Morgan,  T.  H. 

'93.         Experimental  Studies  on  the  Teleost  Eggs. 
Anat.  Am.,  Jahrg.  8,  pp.  803-814. 

Morgan,  T.  H. 

'95.         The  Formation  of  the  Fish  Embryo. 

Journ.  Morph.,  Vol.  X,  pp.  419-472,  pi.  XXIII-XXV. 


SUMNER:   KUPFFEK'S  VESICLE  83 

Oellacher,  J. 

'72.          Beitrage   zur    Entwicklungsgeschichte  der  Knochcnfisclie   nach   Beobachtungen   am 

Bachforelleneie. 
Zeitschr.f.  wiss.  ZooL,  Bd.  22,  pp.  373-421,  Taf.  XXXII,  XXXIII. 

Raffaelle,  F. 

'88.          Le  uova  galleggianti  e  le  larve  del  Teleostei  nel  golfo  di  Napoli. 

Mitth.  aus  der  Zool.  Station  zu  JVeapel,  Bd.  8,  pp.  1—84,  pi.  1-5. 

Reinhard,  W. 

'98.          Die  Bedeutung  des  Periblastes  und  der  Kupffer'schen  Blase  in  der  Entwiokelung  der 

Knoehenfisclie. 
Arch./,  mikr.  Anat.,  1898,  pp.  793-819,  Taf.  XXXV-XXXVI. 

Ryder,  J.  A. 

'86.         On  the  Development  of  Osseous  Fishes. 

Rep.  of  U.  S.  Fish  Com.  for  1885,  pp.  116,  pi.  XXX. 
Schwarz,  D. 

'89.          Untersuchungen  des  Schwanzes  bei  den  Embryonen  der  Wirbelthiere. 
Zeitschr.  f.  wiss.  ZooL,  Bd.  48,  pp.  191-223,  Taf.  XII-XIV. 

Sobotta,  J. 

'96.         Die  Gastrulation  von  Amia  calva. 

Verh.  d.  anat.  Ges.,  1896,  pp.  108-111. 

Sobotta,  J. 

'98.          Die  morphologische  Bedeutung  der  Kupffer'schen  Blase. 

Verh.  d.  phys.  med.  Ges.  zu  Wurzburg,  Bd.  XXXII,  pp.  16,  1  pi. 

Sumner,  F.  B. 

(See  below.) 

Virchow,  H. 

'95.          Ueber  das  Keimhautrand  der  Salmoniden. 
Verh.  d.  anat.  Ges.,  1895,  pp.  201-219. 

Wilson,  H.  V. 

'91.          The  Embryology  of  the  Sea  Bass  (Serranus  atrarius). 

Bull.  U.  S.  Fish  Com.  for  1889,  pp.  209-277,  pi.  LXXXVIII-CVII. 


The  following  is  a  list  of  brief  abstracts  of  papers  read  by  the  author  of  the  pres- 
ent memoir  and  referred  to  in  the  text  : 

1.  1899  a.  On  the  Early  Development  of  the  Catfish  (Noturus).     Read  before  Amer.  Mbrph. 

>Soc.  Dec.  28,  1898. 

Abstracted  in  Science,  Mar.  3,  1899,  pp.  313,  314.  (No  mention  is  made  in  the  ab- 
stract of  the  "  prostomal  thickening "  of  the  blastoderm,  although  this  appearance 
was  described  in  the  paper.) 


84 


MEMOIRS  OF  THE  NEW  YORK   ACADEMY  OF  SCIENCES 


2.  1899  b.  Observations  on  the  Germ-layers  of  Teleost  Fishes.     Head  before  Section  of  jBi 

JV:  Y.  Acad.  Sci.,  Mar.  14,  1899 
Abstracted  in  Science,  May  19,  1899,  p.  718. 

3.  1900  a.    The  Teleost  Gastrula  and  its  Modifications.     Head  before  Arncr.  Morph.  Soc.  Dec. 

27,  1899. 
Abstracted  in  Science,  Feb.  2,  1900,  p.  169. 

4.  1900  b.    Kupffer's  Vesicle  and  its  relation  to  Gastrnlation  and  Concrescence.     Read  before 

Section  of  Biology,  N.  Y.  Acad.  Sci.,  Feb.  12,  1900. 
Abstracted  in  Science,  Mar.  16,  1900. 


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on  the  date  to  which  renewed. 
Renewed  books  are  subject  to  immediate  recall. 

OCT  2  7  1961 

Oc31'61ST 

^^\Q<^-^ 

/jbifc- 

W~^M96! 

VI  V  ^9Sj 

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U   K/*W-    ) 
\  /p 

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OECl3^1' 

r:ci»^si 

-    : 

JAN  2  5..J962 

T  ^  01    en     f  tan                               General  Library 

I'D  21-50m-6,  60                                  TTnivcreirv  nf  Talifrirnia 

(B1321slO)476                                       Berkeley 

299388 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


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